Pasha decided to invite his friends to a tea party. For that occasion, he has a large teapot with the capacity of w milliliters and 2n tea cups, each cup is for one of Pasha's friends. The i-th cup can hold at most ai milliliters of water.It turned out that among Pasha's friends there are exactly n boys and exactly n girls and all of them are going to come to the tea party. To please everyone, Pasha decided to pour the water for the tea as follows:  Pasha can boil the teapot exactly once by pouring there at most w milliliters of water;  Pasha pours the same amount of water to each girl;  Pasha pours the same amount of water to each boy;  if each girl gets x milliliters of water, then each boy gets 2x milliliters of water. In the other words, each boy should get two times more water than each girl does.Pasha is very kind and polite, so he wants to maximize the total amount of the water that he pours to his friends. Your task is to help him and determine the optimum distribution of cups between Pasha's friends.

The first line of the input contains two integers, n and w (1 ≤ n ≤ 105, 1 ≤ w ≤ 109) — the number of Pasha's friends that are boys (equal to the number of Pasha's friends that are girls) and the capacity of Pasha's teapot in milliliters. The second line of the input contains the sequence of integers ai (1 ≤ ai ≤ 109, 1 ≤ i ≤ 2n) — the capacities of Pasha's tea cups in milliliters.

Print a single real number — the maximum total amount of water in milliliters that Pasha can pour to his friends without violating the given conditions. Your answer will be considered correct if its absolute or relative error doesn't exceed 10 - 6.

NotePasha also has candies that he is going to give to girls but that is another task...

function ProblemSolver() {
    this.HAS_TEST_CASES = false ;
    this.INPUT_FILE_NAME = "sample.in" ;
    this.OUTPUT_FILE_NAME = "sample.out" ;
    this.DO_OUTPUT_TO_FILE = false ;
    this.CLEAR_ARRAY_PER_CASE = false ;

    this.solveCase = function() {
        var res , i , j , fl , cn , a , b , c , lo , hi , mi , eps ;
        this.arr = this.arr.sort( function( le , ri ) { return le - ri ; } ) ;
        res = 0 ;
        lo = 0.0 ;
        hi = this.arr[ 0 ] * 1.0 ;
        eps = 1e-11 ;
        cn = 1000 ;
        while( ( hi - lo ) >= eps && cn-- > 0 ) {
            mi = ( lo + hi ) / 2.0 ;
            a = 2.0 * mi ;
            if( mi < this.arr[ 0 ] + eps && a < this.arr[ this.n ] + eps && mi + a < ( this.w / this.n ) + eps ) {
                lo = mi ;
                res = mi * this.n + a * this.n ;
            }
            else {
                hi = mi ;
            }
        }
        print( res.toFixed( 10 ) ) ;
    } ;

    this.init = function() {
        this.lim1 = 100010 ;
        this.lim2 = 110 ;
        this.cc = 1 ;
        this.ind = 1 ;
        this.n = 0 ;
        this.cn = 0 ;
        this.declareAndFillArrays() ;
    } ;

    this.getInput = function( irObj ) {
        var hasMoreInput , i ;
        hasMoreInput = true ;
        try {
        	this.n = irObj.nextInt() ;
        	this.w = irObj.nextInt() ;
            this.arr = [] ;
            for( i = 0 ; i < 2 * this.n ; i++ ) {
                this.arr.push( irObj.nextInt() ) ;
            }
        }
        catch( ex ) {
            hasMoreInput = false ;
        }
        return hasMoreInput ;
    } ;

    this.clearArraysPerCase = function() {
        var i ;
        this.arr = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.arr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
    } ;

    this.clearPerCase = function() {
        this.cn = 0 ;
        this.cc++ ;
        if( this.CLEAR_ARRAY_PER_CASE == true ) {
            this.clearArraysPerCase() ;
        }
    } ;

    this.declareAndFillArrays = function() {
        var i , j ;
        this.srr = new Array() ;
        this.vis = new Array() ;
        this.arr = new Array() ;
        this.brr = new Array() ;
        this.memo = new Array() ;
        this.done = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.srr.push( '' ) ;
            this.vis.push( 0 ) ;
            this.arr.push( 0 ) ;
            this.brr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
        for( i = 0 ; i < this.lim2 ; i++ ) {
            this.memo.push( new Array() ) ;
            this.done.push( new Array() ) ;
            for( j = 0 ; j < this.lim2 ; j++ ) {
                this.memo[ i ].push( -1 ) ;
                this.done[ i ].push( 0 ) ;
            }
        }
    } ;

    this.init() ;
}

function InputReader() {
    var self = this ;
    this.allLines = new Array() ;
    this.currrentLineNumber = 0 ;
    this.currrentCharacterIndex = 0 ;
    this.callBackFunction = null ;
    this.parentContext = null ;

    this.readAllLines = function() {
        var singleLine ;
        while( true ) {
            try {
                singleLine = readline() ;
                if( singleLine == null ) {
                    break ;
                }
            }
            catch( ex ) {
                break ;
            }
            this.allLines.push( singleLine ) ;
        }
    } ;

    this.readAllLinesFromRhino = function() {
        var brObj , line ;
        importPackage( java.io ) ;
        importPackage( java.lang ) ;
        brObj = new BufferedReader( new InputStreamReader( System[ 'in' ] ) ) ;
        this.allLines = [] ;
        while( true ) {
            line = brObj.readLine() ;
            if( line == null ) {
                break;
            }
            this.allLines.push( line ) ;
        }
    } ;

    this.readSingleLinesFromNodeJsJudgeServer = function( chunk ) {
        self.chunkData += chunk ;
    } ;

    this.readEndFromNodeJsJudgeServer = function() {
        self.parseRawData( self.chunkData ) ;
        self.parentContext.runCases() ;
    } ;

    this.readAllLinesFromNodeJsJudgeServer = function( parentContext ) {
        this.parentContext = parentContext ;
        process.stdin.resume() ;
        process.stdin.setEncoding( 'utf8' ) ;
        this.chunkData = '' ;
        process.stdin.on( 'data' , this.readSingleLinesFromNodeJsJudgeServer ) ;
        process.stdin.on( 'end' , this.readEndFromNodeJsJudgeServer ) ;
    } ;

    this.parseRawData = function( data ) {
        var len , i , currentString ;
        len = data.length ;
        currentString = '' ;
        this.allLines = [] ;
        for( i = 0 ; i < len ; i++ ) {
            if( data[ i ] == '\r' ) {
            }
            else if( data[ i ] == '\n' ) {
                this.allLines.push( currentString ) ;
                currentString = '' ;
            }
            else {
                currentString += data[ i ] ;
            }
        }
        if( currentString != '' ) {
            this.allLines.push( currentString ) ;
        }
    } ;

    this.readAllLinesFromFile = function( inputFileName ) {
        var currentDirectory , fsObj , inputFilePath , rawData ;
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            inputFilePath = currentDirectory + '\\' + inputFileName ;
        }
        else {
            //on linux
            inputFilePath = currentDirectory + '/' + inputFileName ;
        }
        rawData = fsObj.readFileSync( inputFilePath , "utf8" ) ;
        this.parseRawData( rawData ) ;
    } ;

    this.next = function( flag ) {
        var len , i , startIdx , res , endIdx ;
        if( flag == 0 ) {
            if( this.currrentCharacterIndex != 0 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            res = '' ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
            }
            this.currrentLineNumber++ ;
            this.currrentCharacterIndex = 0 ;
            return res ;
        }
        while( true ) {
            if( this.currrentLineNumber >= this.allLines.length ) {
                throw new Error( 'No more tokens available!' ) ;
            }
            startIdx = -1 ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) != ' '.charCodeAt( 0 ) ) {
                    startIdx = i ;
                    break ;
                }
            }
            if( startIdx == -1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
                continue ;
            }
            res = '' ;
            endIdx = len - 1 ;
            for( i = startIdx ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) == ' '.charCodeAt( 0 ) ) {
                    endIdx = i ;
                    break ;
                }
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) >= 48 && this.allLines[ this.currrentLineNumber ].charCodeAt( i ) <= 57 ) {
                    res += '' + ( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) - 48 ) ;
                }
                else {
                    res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
                }
            }
            this.currrentCharacterIndex = endIdx ;
            if( endIdx == len - 1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            return res ;
        }
    } ;

    this.nextInt = function() {
        return parseInt( this.next( 1 ) ) ;
    } ;

    this.nextDouble = function() {
        return parseFloat( this.next( 1 ) ) ;
    } ;

    this.nextString = function() {
        return this.next( 1 ) ;
    } ;

    this.nextLine = function() {
        return this.next( 0 ) ;
    } ;
}

function FileOutputHandler() {
    this.resultantStringArray = new Array() ;

    this.addNewLine = function( newString ) {
        this.resultantStringArray.push( newString ) ;
    } ;

    this.clearPercase = function() {
        this.resultantStringArray = new Array() ;
    } ;

    this.flushOutOutputToFile = function( outputFileName ) {
        var i , sz , res , currentDirectory , fsObj , outputFilePath ;
        res = '' ;
        sz = this.resultantStringArray.length ;
        for( i = 0 ; i < sz ; i++ ) {
            if( i != 0 ) {
                res += '\n' ;
            }
            res += this.resultantStringArray[ i ] ;
        }
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            outputFilePath = currentDirectory + '\\' + outputFileName ;
        }
        else {
            //on linux
            outputFilePath = currentDirectory + '/' + outputFileName ;
        }
        fsObj.writeFileSync( outputFilePath , res ) ;
        this.clearPercase() ;
    } ;
}

function CodeExecutioner() {
    this.irObj = new InputReader() ;
    this.psObj = new ProblemSolver() ;
    this.fohObj = new FileOutputHandler() ;

    this.runCases = function() {
		var testCases , hasMoreTestCases , i ;
        if( this.psObj.HAS_TEST_CASES == true ) {
            testCases = this.irObj.nextInt() ;
            for( i = 0 ; i < testCases ; i++ ) {
                this.psObj.clearPerCase() ;
                this.psObj.getInput( this.irObj ) ;
                this.psObj.solveCase() ;
            }
        }
        else {
            while( true ) {
                this.psObj.clearPerCase() ;
                hasMoreTestCases = this.psObj.getInput( this.irObj ) ;
                if( hasMoreTestCases == false ) {
                    break;
                }
                this.psObj.solveCase() ;
            }
        }
        if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
            this.fohObj.flushOutOutputToFile( this.psObj.OUTPUT_FILE_NAME ) ;
        }
    } ;

    this.detectEnvironmentType = function() {
        var environmentType = null ;
        try {
            if( importPackage != null ) {
                environmentType = 'rhino' ;
            }
        }
        catch( ex1 ) {
            try {
                //for nodejs local server check
                if( __dirname != null && ( __dirname.indexOf( 'D:') != -1 || __dirname.indexOf( '/media/') != -1 ) ) {
                    environmentType = 'local-node-js' ;
                }
                else {
                    environmentType = 'server-node-js' ;
                }
            }
            catch( ex2 ) {
                try {
                    if( readline == null || typeof( readline ) != 'function' ) {
                        environmentType = 'server-node-js' ;
                    }
                    else {
                        try {
                            if( Map != null ) {
                                environmentType = 'spider-monkey' ;
                            }
                            else {
                                environmentType = 'javascript-v8' ;
                            }
                        }
                        catch( ex3 ) {
                            environmentType = 'javascript-v8' ;
                        }
                    }
                }
                catch( ex3 ) {
                    environmentType = 'server-node-js' ;
                }
            }
        }
        return environmentType ;
    } ;

    this.configureStreamsAndReadInput = function() {
        var localContext , isNodeJsJudgeServer , environmentType ;
        isNodeJsJudgeServer = false ;
        environmentType = this.detectEnvironmentType() ;
        if( environmentType == 'local-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
                localContext = this.fohObj ;
                print = function() {
                    localContext.addNewLine.apply( localContext , arguments ) ;
                }
            }
            this.irObj.readAllLinesFromFile( this.psObj.INPUT_FILE_NAME ) ;
            this.runCases() ;
        }
        else if( environmentType == 'server-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            this.irObj.readAllLinesFromNodeJsJudgeServer( this ) ;
        }
        else if( environmentType == 'javascript-v8' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
        else if( environmentType == 'rhino' ) {
            this.irObj.readAllLinesFromRhino() ;
            this.runCases() ;
        }
        else if( environmentType == 'spider-monkey' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
    } ;

    this.configureStreamsAndReadInput() ;
}

new CodeExecutioner() ;

function ProblemSolver() {
    this.HAS_TEST_CASES = false ;
    this.INPUT_FILE_NAME = "sample.in" ;
    this.OUTPUT_FILE_NAME = "sample.out" ;
    this.DO_OUTPUT_TO_FILE = false ;
    this.CLEAR_ARRAY_PER_CASE = false ;

    this.solveCase = function() {
        var res , i , j , fl , cn , a , b , c , lo , hi , mi , eps ;
        this.arr = this.arr.sort( function( le , ri ) { return le - ri ; } ) ;
        res = 0 ;
        lo = 0.0 ;
        hi = this.arr[ 0 ] * 1.0 ;
        eps = 1e-12 ;
        cn = 1000 ;
        while( ( hi - lo ) >= eps && cn-- > 0 ) {
            mi = ( lo + hi ) / 2.0 ;
            a = 2.0 * mi ;
            if( mi < this.arr[ 0 ] + eps && a < this.arr[ this.n ] + eps && mi + a < ( this.w / this.n ) + eps ) {
                lo = mi ;
                res = mi * this.n + a * this.n ;
            }
            else {
                hi = mi ;
            }
        }
        print( res.toFixed( 10 ) ) ;
    } ;

    this.init = function() {
        this.lim1 = 100010 ;
        this.lim2 = 110 ;
        this.cc = 1 ;
        this.ind = 1 ;
        this.n = 0 ;
        this.cn = 0 ;
        this.declareAndFillArrays() ;
    } ;

    this.getInput = function( irObj ) {
        var hasMoreInput , i ;
        hasMoreInput = true ;
        try {
        	this.n = irObj.nextInt() ;
        	this.w = irObj.nextInt() ;
            this.arr = [] ;
            for( i = 0 ; i < 2 * this.n ; i++ ) {
                this.arr.push( irObj.nextInt() ) ;
            }
        }
        catch( ex ) {
            hasMoreInput = false ;
        }
        return hasMoreInput ;
    } ;

    this.clearArraysPerCase = function() {
        var i ;
        this.arr = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.arr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
    } ;

    this.clearPerCase = function() {
        this.cn = 0 ;
        this.cc++ ;
        if( this.CLEAR_ARRAY_PER_CASE == true ) {
            this.clearArraysPerCase() ;
        }
    } ;

    this.declareAndFillArrays = function() {
        var i , j ;
        this.srr = new Array() ;
        this.vis = new Array() ;
        this.arr = new Array() ;
        this.brr = new Array() ;
        this.memo = new Array() ;
        this.done = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.srr.push( '' ) ;
            this.vis.push( 0 ) ;
            this.arr.push( 0 ) ;
            this.brr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
        for( i = 0 ; i < this.lim2 ; i++ ) {
            this.memo.push( new Array() ) ;
            this.done.push( new Array() ) ;
            for( j = 0 ; j < this.lim2 ; j++ ) {
                this.memo[ i ].push( -1 ) ;
                this.done[ i ].push( 0 ) ;
            }
        }
    } ;

    this.init() ;
}

function InputReader() {
    var self = this ;
    this.allLines = new Array() ;
    this.currrentLineNumber = 0 ;
    this.currrentCharacterIndex = 0 ;
    this.callBackFunction = null ;
    this.parentContext = null ;

    this.readAllLines = function() {
        var singleLine ;
        while( true ) {
            try {
                singleLine = readline() ;
                if( singleLine == null ) {
                    break ;
                }
            }
            catch( ex ) {
                break ;
            }
            this.allLines.push( singleLine ) ;
        }
    } ;

    this.readAllLinesFromRhino = function() {
        var brObj , line ;
        importPackage( java.io ) ;
        importPackage( java.lang ) ;
        brObj = new BufferedReader( new InputStreamReader( System[ 'in' ] ) ) ;
        this.allLines = [] ;
        while( true ) {
            line = brObj.readLine() ;
            if( line == null ) {
                break;
            }
            this.allLines.push( line ) ;
        }
    } ;

    this.readSingleLinesFromNodeJsJudgeServer = function( chunk ) {
        self.chunkData += chunk ;
    } ;

    this.readEndFromNodeJsJudgeServer = function() {
        self.parseRawData( self.chunkData ) ;
        self.parentContext.runCases() ;
    } ;

    this.readAllLinesFromNodeJsJudgeServer = function( parentContext ) {
        this.parentContext = parentContext ;
        process.stdin.resume() ;
        process.stdin.setEncoding( 'utf8' ) ;
        this.chunkData = '' ;
        process.stdin.on( 'data' , this.readSingleLinesFromNodeJsJudgeServer ) ;
        process.stdin.on( 'end' , this.readEndFromNodeJsJudgeServer ) ;
    } ;

    this.parseRawData = function( data ) {
        var len , i , currentString ;
        len = data.length ;
        currentString = '' ;
        this.allLines = [] ;
        for( i = 0 ; i < len ; i++ ) {
            if( data[ i ] == '\r' ) {
            }
            else if( data[ i ] == '\n' ) {
                this.allLines.push( currentString ) ;
                currentString = '' ;
            }
            else {
                currentString += data[ i ] ;
            }
        }
        if( currentString != '' ) {
            this.allLines.push( currentString ) ;
        }
    } ;

    this.readAllLinesFromFile = function( inputFileName ) {
        var currentDirectory , fsObj , inputFilePath , rawData ;
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            inputFilePath = currentDirectory + '\\' + inputFileName ;
        }
        else {
            //on linux
            inputFilePath = currentDirectory + '/' + inputFileName ;
        }
        rawData = fsObj.readFileSync( inputFilePath , "utf8" ) ;
        this.parseRawData( rawData ) ;
    } ;

    this.next = function( flag ) {
        var len , i , startIdx , res , endIdx ;
        if( flag == 0 ) {
            if( this.currrentCharacterIndex != 0 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            res = '' ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
            }
            this.currrentLineNumber++ ;
            this.currrentCharacterIndex = 0 ;
            return res ;
        }
        while( true ) {
            if( this.currrentLineNumber >= this.allLines.length ) {
                throw new Error( 'No more tokens available!' ) ;
            }
            startIdx = -1 ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) != ' '.charCodeAt( 0 ) ) {
                    startIdx = i ;
                    break ;
                }
            }
            if( startIdx == -1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
                continue ;
            }
            res = '' ;
            endIdx = len - 1 ;
            for( i = startIdx ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) == ' '.charCodeAt( 0 ) ) {
                    endIdx = i ;
                    break ;
                }
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) >= 48 && this.allLines[ this.currrentLineNumber ].charCodeAt( i ) <= 57 ) {
                    res += '' + ( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) - 48 ) ;
                }
                else {
                    res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
                }
            }
            this.currrentCharacterIndex = endIdx ;
            if( endIdx == len - 1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            return res ;
        }
    } ;

    this.nextInt = function() {
        return parseInt( this.next( 1 ) ) ;
    } ;

    this.nextDouble = function() {
        return parseFloat( this.next( 1 ) ) ;
    } ;

    this.nextString = function() {
        return this.next( 1 ) ;
    } ;

    this.nextLine = function() {
        return this.next( 0 ) ;
    } ;
}

function FileOutputHandler() {
    this.resultantStringArray = new Array() ;

    this.addNewLine = function( newString ) {
        this.resultantStringArray.push( newString ) ;
    } ;

    this.clearPercase = function() {
        this.resultantStringArray = new Array() ;
    } ;

    this.flushOutOutputToFile = function( outputFileName ) {
        var i , sz , res , currentDirectory , fsObj , outputFilePath ;
        res = '' ;
        sz = this.resultantStringArray.length ;
        for( i = 0 ; i < sz ; i++ ) {
            if( i != 0 ) {
                res += '\n' ;
            }
            res += this.resultantStringArray[ i ] ;
        }
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            outputFilePath = currentDirectory + '\\' + outputFileName ;
        }
        else {
            //on linux
            outputFilePath = currentDirectory + '/' + outputFileName ;
        }
        fsObj.writeFileSync( outputFilePath , res ) ;
        this.clearPercase() ;
    } ;
}

function CodeExecutioner() {
    this.irObj = new InputReader() ;
    this.psObj = new ProblemSolver() ;
    this.fohObj = new FileOutputHandler() ;

    this.runCases = function() {
		var testCases , hasMoreTestCases , i ;
        if( this.psObj.HAS_TEST_CASES == true ) {
            testCases = this.irObj.nextInt() ;
            for( i = 0 ; i < testCases ; i++ ) {
                this.psObj.clearPerCase() ;
                this.psObj.getInput( this.irObj ) ;
                this.psObj.solveCase() ;
            }
        }
        else {
            while( true ) {
                this.psObj.clearPerCase() ;
                hasMoreTestCases = this.psObj.getInput( this.irObj ) ;
                if( hasMoreTestCases == false ) {
                    break;
                }
                this.psObj.solveCase() ;
            }
        }
        if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
            this.fohObj.flushOutOutputToFile( this.psObj.OUTPUT_FILE_NAME ) ;
        }
    } ;

    this.detectEnvironmentType = function() {
        var environmentType = null ;
        try {
            if( importPackage != null ) {
                environmentType = 'rhino' ;
            }
        }
        catch( ex1 ) {
            try {
                //for nodejs local server check
                if( __dirname != null && ( __dirname.indexOf( 'D:') != -1 || __dirname.indexOf( '/media/') != -1 ) ) {
                    environmentType = 'local-node-js' ;
                }
                else {
                    environmentType = 'server-node-js' ;
                }
            }
            catch( ex2 ) {
                try {
                    if( readline == null || typeof( readline ) != 'function' ) {
                        environmentType = 'server-node-js' ;
                    }
                    else {
                        try {
                            if( Map != null ) {
                                environmentType = 'spider-monkey' ;
                            }
                            else {
                                environmentType = 'javascript-v8' ;
                            }
                        }
                        catch( ex3 ) {
                            environmentType = 'javascript-v8' ;
                        }
                    }
                }
                catch( ex3 ) {
                    environmentType = 'server-node-js' ;
                }
            }
        }
        return environmentType ;
    } ;

    this.configureStreamsAndReadInput = function() {
        var localContext , isNodeJsJudgeServer , environmentType ;
        isNodeJsJudgeServer = false ;
        environmentType = this.detectEnvironmentType() ;
        if( environmentType == 'local-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
                localContext = this.fohObj ;
                print = function() {
                    localContext.addNewLine.apply( localContext , arguments ) ;
                }
            }
            this.irObj.readAllLinesFromFile( this.psObj.INPUT_FILE_NAME ) ;
            this.runCases() ;
        }
        else if( environmentType == 'server-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            this.irObj.readAllLinesFromNodeJsJudgeServer( this ) ;
        }
        else if( environmentType == 'javascript-v8' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
        else if( environmentType == 'rhino' ) {
            this.irObj.readAllLinesFromRhino() ;
            this.runCases() ;
        }
        else if( environmentType == 'spider-monkey' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
    } ;

    this.configureStreamsAndReadInput() ;
}

new CodeExecutioner() ;

function ProblemSolver() {
    this.HAS_TEST_CASES = false ;
    this.INPUT_FILE_NAME = "sample.in" ;
    this.OUTPUT_FILE_NAME = "sample.out" ;
    this.DO_OUTPUT_TO_FILE = false ;
    this.CLEAR_ARRAY_PER_CASE = false ;

    this.solveCase = function() {
        var res , i , j , fl , cn , a , b , c , lo , hi , mi , eps ;
        this.arr = this.arr.sort( function( le , ri ) { return le - ri ; } ) ;
        res = 0 ;
        lo = 0.0 ;
        hi = this.arr[ 0 ] * 1.0 ;
        eps = 1e-11 ;
        cn = 100 ;
        while( ( hi - lo ) >= eps && cn-- > 0 ) {
            mi = ( lo + hi ) / 2.0 ;
            a = 2.0 * mi ;
            if( mi < this.arr[ 0 ] + eps && a < this.arr[ this.n ] + eps && mi * this.n + a * this.n < this.w + eps ) {
                lo = mi ;
                res = mi * this.n + a * this.n ;
            }
            else {
                hi = mi ;
            }
        }
        print( res.toFixed( 10 ) ) ;
    } ;

    this.init = function() {
        this.lim1 = 100010 ;
        this.lim2 = 110 ;
        this.cc = 1 ;
        this.ind = 1 ;
        this.n = 0 ;
        this.cn = 0 ;
        this.declareAndFillArrays() ;
    } ;

    this.getInput = function( irObj ) {
        var hasMoreInput , i ;
        hasMoreInput = true ;
        try {
        	this.n = irObj.nextInt() ;
        	this.w = irObj.nextInt() ;
            this.arr = [] ;
            for( i = 0 ; i < 2 * this.n ; i++ ) {
                this.arr.push( irObj.nextInt() ) ;
            }
        }
        catch( ex ) {
            hasMoreInput = false ;
        }
        return hasMoreInput ;
    } ;

    this.clearArraysPerCase = function() {
        var i ;
        this.arr = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.arr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
    } ;

    this.clearPerCase = function() {
        this.cn = 0 ;
        this.cc++ ;
        if( this.CLEAR_ARRAY_PER_CASE == true ) {
            this.clearArraysPerCase() ;
        }
    } ;

    this.declareAndFillArrays = function() {
        var i , j ;
        this.srr = new Array() ;
        this.vis = new Array() ;
        this.arr = new Array() ;
        this.brr = new Array() ;
        this.memo = new Array() ;
        this.done = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.srr.push( '' ) ;
            this.vis.push( 0 ) ;
            this.arr.push( 0 ) ;
            this.brr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
        for( i = 0 ; i < this.lim2 ; i++ ) {
            this.memo.push( new Array() ) ;
            this.done.push( new Array() ) ;
            for( j = 0 ; j < this.lim2 ; j++ ) {
                this.memo[ i ].push( -1 ) ;
                this.done[ i ].push( 0 ) ;
            }
        }
    } ;

    this.init() ;
}

function InputReader() {
    var self = this ;
    this.allLines = new Array() ;
    this.currrentLineNumber = 0 ;
    this.currrentCharacterIndex = 0 ;
    this.callBackFunction = null ;
    this.parentContext = null ;

    this.readAllLines = function() {
        var singleLine ;
        while( true ) {
            try {
                singleLine = readline() ;
                if( singleLine == null ) {
                    break ;
                }
            }
            catch( ex ) {
                break ;
            }
            this.allLines.push( singleLine ) ;
        }
    } ;

    this.readAllLinesFromRhino = function() {
        var brObj , line ;
        importPackage( java.io ) ;
        importPackage( java.lang ) ;
        brObj = new BufferedReader( new InputStreamReader( System[ 'in' ] ) ) ;
        this.allLines = [] ;
        while( true ) {
            line = brObj.readLine() ;
            if( line == null ) {
                break;
            }
            this.allLines.push( line ) ;
        }
    } ;

    this.readSingleLinesFromNodeJsJudgeServer = function( chunk ) {
        self.chunkData += chunk ;
    } ;

    this.readEndFromNodeJsJudgeServer = function() {
        self.parseRawData( self.chunkData ) ;
        self.parentContext.runCases() ;
    } ;

    this.readAllLinesFromNodeJsJudgeServer = function( parentContext ) {
        this.parentContext = parentContext ;
        process.stdin.resume() ;
        process.stdin.setEncoding( 'utf8' ) ;
        this.chunkData = '' ;
        process.stdin.on( 'data' , this.readSingleLinesFromNodeJsJudgeServer ) ;
        process.stdin.on( 'end' , this.readEndFromNodeJsJudgeServer ) ;
    } ;

    this.parseRawData = function( data ) {
        var len , i , currentString ;
        len = data.length ;
        currentString = '' ;
        this.allLines = [] ;
        for( i = 0 ; i < len ; i++ ) {
            if( data[ i ] == '\r' ) {
            }
            else if( data[ i ] == '\n' ) {
                this.allLines.push( currentString ) ;
                currentString = '' ;
            }
            else {
                currentString += data[ i ] ;
            }
        }
        if( currentString != '' ) {
            this.allLines.push( currentString ) ;
        }
    } ;

    this.readAllLinesFromFile = function( inputFileName ) {
        var currentDirectory , fsObj , inputFilePath , rawData ;
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            inputFilePath = currentDirectory + '\\' + inputFileName ;
        }
        else {
            //on linux
            inputFilePath = currentDirectory + '/' + inputFileName ;
        }
        rawData = fsObj.readFileSync( inputFilePath , "utf8" ) ;
        this.parseRawData( rawData ) ;
    } ;

    this.next = function( flag ) {
        var len , i , startIdx , res , endIdx ;
        if( flag == 0 ) {
            if( this.currrentCharacterIndex != 0 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            res = '' ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
            }
            this.currrentLineNumber++ ;
            this.currrentCharacterIndex = 0 ;
            return res ;
        }
        while( true ) {
            if( this.currrentLineNumber >= this.allLines.length ) {
                throw new Error( 'No more tokens available!' ) ;
            }
            startIdx = -1 ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) != ' '.charCodeAt( 0 ) ) {
                    startIdx = i ;
                    break ;
                }
            }
            if( startIdx == -1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
                continue ;
            }
            res = '' ;
            endIdx = len - 1 ;
            for( i = startIdx ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) == ' '.charCodeAt( 0 ) ) {
                    endIdx = i ;
                    break ;
                }
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) >= 48 && this.allLines[ this.currrentLineNumber ].charCodeAt( i ) <= 57 ) {
                    res += '' + ( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) - 48 ) ;
                }
                else {
                    res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
                }
            }
            this.currrentCharacterIndex = endIdx ;
            if( endIdx == len - 1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            return res ;
        }
    } ;

    this.nextInt = function() {
        return parseInt( this.next( 1 ) ) ;
    } ;

    this.nextDouble = function() {
        return parseFloat( this.next( 1 ) ) ;
    } ;

    this.nextString = function() {
        return this.next( 1 ) ;
    } ;

    this.nextLine = function() {
        return this.next( 0 ) ;
    } ;
}

function FileOutputHandler() {
    this.resultantStringArray = new Array() ;

    this.addNewLine = function( newString ) {
        this.resultantStringArray.push( newString ) ;
    } ;

    this.clearPercase = function() {
        this.resultantStringArray = new Array() ;
    } ;

    this.flushOutOutputToFile = function( outputFileName ) {
        var i , sz , res , currentDirectory , fsObj , outputFilePath ;
        res = '' ;
        sz = this.resultantStringArray.length ;
        for( i = 0 ; i < sz ; i++ ) {
            if( i != 0 ) {
                res += '\n' ;
            }
            res += this.resultantStringArray[ i ] ;
        }
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            outputFilePath = currentDirectory + '\\' + outputFileName ;
        }
        else {
            //on linux
            outputFilePath = currentDirectory + '/' + outputFileName ;
        }
        fsObj.writeFileSync( outputFilePath , res ) ;
        this.clearPercase() ;
    } ;
}

function CodeExecutioner() {
    this.irObj = new InputReader() ;
    this.psObj = new ProblemSolver() ;
    this.fohObj = new FileOutputHandler() ;

    this.runCases = function() {
		var testCases , hasMoreTestCases , i ;
        if( this.psObj.HAS_TEST_CASES == true ) {
            testCases = this.irObj.nextInt() ;
            for( i = 0 ; i < testCases ; i++ ) {
                this.psObj.clearPerCase() ;
                this.psObj.getInput( this.irObj ) ;
                this.psObj.solveCase() ;
            }
        }
        else {
            while( true ) {
                this.psObj.clearPerCase() ;
                hasMoreTestCases = this.psObj.getInput( this.irObj ) ;
                if( hasMoreTestCases == false ) {
                    break;
                }
                this.psObj.solveCase() ;
            }
        }
        if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
            this.fohObj.flushOutOutputToFile( this.psObj.OUTPUT_FILE_NAME ) ;
        }
    } ;

    this.detectEnvironmentType = function() {
        var environmentType = null ;
        try {
            if( importPackage != null ) {
                environmentType = 'rhino' ;
            }
        }
        catch( ex1 ) {
            try {
                //for nodejs local server check
                if( __dirname != null && ( __dirname.indexOf( 'D:') != -1 || __dirname.indexOf( '/media/') != -1 ) ) {
                    environmentType = 'local-node-js' ;
                }
                else {
                    environmentType = 'server-node-js' ;
                }
            }
            catch( ex2 ) {
                try {
                    if( readline == null || typeof( readline ) != 'function' ) {
                        environmentType = 'server-node-js' ;
                    }
                    else {
                        try {
                            if( Map != null ) {
                                environmentType = 'spider-monkey' ;
                            }
                            else {
                                environmentType = 'javascript-v8' ;
                            }
                        }
                        catch( ex3 ) {
                            environmentType = 'javascript-v8' ;
                        }
                    }
                }
                catch( ex3 ) {
                    environmentType = 'server-node-js' ;
                }
            }
        }
        return environmentType ;
    } ;

    this.configureStreamsAndReadInput = function() {
        var localContext , isNodeJsJudgeServer , environmentType ;
        isNodeJsJudgeServer = false ;
        environmentType = this.detectEnvironmentType() ;
        if( environmentType == 'local-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
                localContext = this.fohObj ;
                print = function() {
                    localContext.addNewLine.apply( localContext , arguments ) ;
                }
            }
            this.irObj.readAllLinesFromFile( this.psObj.INPUT_FILE_NAME ) ;
            this.runCases() ;
        }
        else if( environmentType == 'server-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            this.irObj.readAllLinesFromNodeJsJudgeServer( this ) ;
        }
        else if( environmentType == 'javascript-v8' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
        else if( environmentType == 'rhino' ) {
            this.irObj.readAllLinesFromRhino() ;
            this.runCases() ;
        }
        else if( environmentType == 'spider-monkey' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
    } ;

    this.configureStreamsAndReadInput() ;
}

new CodeExecutioner() ;

function ProblemSolver() {
    this.HAS_TEST_CASES = false ;
    this.INPUT_FILE_NAME = "sample.in" ;
    this.OUTPUT_FILE_NAME = "sample.out" ;
    this.DO_OUTPUT_TO_FILE = false ;
    this.CLEAR_ARRAY_PER_CASE = false ;

    this.solveCase = function() {
        var res , i , j , fl , cn , a , b , c , lo , hi , mi , eps ;
        this.arr = this.arr.sort( function( le , ri ) { return le - ri ; } ) ;
        res = 0 ;
        lo = 0.0 ;
        hi = this.arr[ 0 ] * 1.0 ;
        eps = 1e-11 ;
        cn = 100 ;
        while( ( hi - lo ) >= eps && cn-- > 0 ) {
            mi = ( lo + hi ) / 2.0 ;
            a = 2.0 * mi ;
            if( mi < this.arr[ 0 ] + eps && a < this.arr[ this.n ] + eps && mi + a < ( this.w / this.n ) + eps ) {
                lo = mi ;
                res = mi * this.n + a * this.n ;
            }
            else {
                hi = mi ;
            }
        }
        print( res.toFixed( 10 ) ) ;
    } ;

    this.init = function() {
        this.lim1 = 100010 ;
        this.lim2 = 110 ;
        this.cc = 1 ;
        this.ind = 1 ;
        this.n = 0 ;
        this.cn = 0 ;
        this.declareAndFillArrays() ;
    } ;

    this.getInput = function( irObj ) {
        var hasMoreInput , i ;
        hasMoreInput = true ;
        try {
        	this.n = irObj.nextInt() ;
        	this.w = irObj.nextInt() ;
            this.arr = [] ;
            for( i = 0 ; i < 2 * this.n ; i++ ) {
                this.arr.push( irObj.nextInt() ) ;
            }
        }
        catch( ex ) {
            hasMoreInput = false ;
        }
        return hasMoreInput ;
    } ;

    this.clearArraysPerCase = function() {
        var i ;
        this.arr = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.arr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
    } ;

    this.clearPerCase = function() {
        this.cn = 0 ;
        this.cc++ ;
        if( this.CLEAR_ARRAY_PER_CASE == true ) {
            this.clearArraysPerCase() ;
        }
    } ;

    this.declareAndFillArrays = function() {
        var i , j ;
        this.srr = new Array() ;
        this.vis = new Array() ;
        this.arr = new Array() ;
        this.brr = new Array() ;
        this.memo = new Array() ;
        this.done = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.srr.push( '' ) ;
            this.vis.push( 0 ) ;
            this.arr.push( 0 ) ;
            this.brr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
        for( i = 0 ; i < this.lim2 ; i++ ) {
            this.memo.push( new Array() ) ;
            this.done.push( new Array() ) ;
            for( j = 0 ; j < this.lim2 ; j++ ) {
                this.memo[ i ].push( -1 ) ;
                this.done[ i ].push( 0 ) ;
            }
        }
    } ;

    this.init() ;
}

function InputReader() {
    var self = this ;
    this.allLines = new Array() ;
    this.currrentLineNumber = 0 ;
    this.currrentCharacterIndex = 0 ;
    this.callBackFunction = null ;
    this.parentContext = null ;

    this.readAllLines = function() {
        var singleLine ;
        while( true ) {
            try {
                singleLine = readline() ;
                if( singleLine == null ) {
                    break ;
                }
            }
            catch( ex ) {
                break ;
            }
            this.allLines.push( singleLine ) ;
        }
    } ;

    this.readAllLinesFromRhino = function() {
        var brObj , line ;
        importPackage( java.io ) ;
        importPackage( java.lang ) ;
        brObj = new BufferedReader( new InputStreamReader( System[ 'in' ] ) ) ;
        this.allLines = [] ;
        while( true ) {
            line = brObj.readLine() ;
            if( line == null ) {
                break;
            }
            this.allLines.push( line ) ;
        }
    } ;

    this.readSingleLinesFromNodeJsJudgeServer = function( chunk ) {
        self.chunkData += chunk ;
    } ;

    this.readEndFromNodeJsJudgeServer = function() {
        self.parseRawData( self.chunkData ) ;
        self.parentContext.runCases() ;
    } ;

    this.readAllLinesFromNodeJsJudgeServer = function( parentContext ) {
        this.parentContext = parentContext ;
        process.stdin.resume() ;
        process.stdin.setEncoding( 'utf8' ) ;
        this.chunkData = '' ;
        process.stdin.on( 'data' , this.readSingleLinesFromNodeJsJudgeServer ) ;
        process.stdin.on( 'end' , this.readEndFromNodeJsJudgeServer ) ;
    } ;

    this.parseRawData = function( data ) {
        var len , i , currentString ;
        len = data.length ;
        currentString = '' ;
        this.allLines = [] ;
        for( i = 0 ; i < len ; i++ ) {
            if( data[ i ] == '\r' ) {
            }
            else if( data[ i ] == '\n' ) {
                this.allLines.push( currentString ) ;
                currentString = '' ;
            }
            else {
                currentString += data[ i ] ;
            }
        }
        if( currentString != '' ) {
            this.allLines.push( currentString ) ;
        }
    } ;

    this.readAllLinesFromFile = function( inputFileName ) {
        var currentDirectory , fsObj , inputFilePath , rawData ;
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            inputFilePath = currentDirectory + '\\' + inputFileName ;
        }
        else {
            //on linux
            inputFilePath = currentDirectory + '/' + inputFileName ;
        }
        rawData = fsObj.readFileSync( inputFilePath , "utf8" ) ;
        this.parseRawData( rawData ) ;
    } ;

    this.next = function( flag ) {
        var len , i , startIdx , res , endIdx ;
        if( flag == 0 ) {
            if( this.currrentCharacterIndex != 0 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            res = '' ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
            }
            this.currrentLineNumber++ ;
            this.currrentCharacterIndex = 0 ;
            return res ;
        }
        while( true ) {
            if( this.currrentLineNumber >= this.allLines.length ) {
                throw new Error( 'No more tokens available!' ) ;
            }
            startIdx = -1 ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) != ' '.charCodeAt( 0 ) ) {
                    startIdx = i ;
                    break ;
                }
            }
            if( startIdx == -1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
                continue ;
            }
            res = '' ;
            endIdx = len - 1 ;
            for( i = startIdx ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) == ' '.charCodeAt( 0 ) ) {
                    endIdx = i ;
                    break ;
                }
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) >= 48 && this.allLines[ this.currrentLineNumber ].charCodeAt( i ) <= 57 ) {
                    res += '' + ( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) - 48 ) ;
                }
                else {
                    res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
                }
            }
            this.currrentCharacterIndex = endIdx ;
            if( endIdx == len - 1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            return res ;
        }
    } ;

    this.nextInt = function() {
        return parseInt( this.next( 1 ) ) ;
    } ;

    this.nextDouble = function() {
        return parseFloat( this.next( 1 ) ) ;
    } ;

    this.nextString = function() {
        return this.next( 1 ) ;
    } ;

    this.nextLine = function() {
        return this.next( 0 ) ;
    } ;
}

function FileOutputHandler() {
    this.resultantStringArray = new Array() ;

    this.addNewLine = function( newString ) {
        this.resultantStringArray.push( newString ) ;
    } ;

    this.clearPercase = function() {
        this.resultantStringArray = new Array() ;
    } ;

    this.flushOutOutputToFile = function( outputFileName ) {
        var i , sz , res , currentDirectory , fsObj , outputFilePath ;
        res = '' ;
        sz = this.resultantStringArray.length ;
        for( i = 0 ; i < sz ; i++ ) {
            if( i != 0 ) {
                res += '\n' ;
            }
            res += this.resultantStringArray[ i ] ;
        }
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            outputFilePath = currentDirectory + '\\' + outputFileName ;
        }
        else {
            //on linux
            outputFilePath = currentDirectory + '/' + outputFileName ;
        }
        fsObj.writeFileSync( outputFilePath , res ) ;
        this.clearPercase() ;
    } ;
}

function CodeExecutioner() {
    this.irObj = new InputReader() ;
    this.psObj = new ProblemSolver() ;
    this.fohObj = new FileOutputHandler() ;

    this.runCases = function() {
		var testCases , hasMoreTestCases , i ;
        if( this.psObj.HAS_TEST_CASES == true ) {
            testCases = this.irObj.nextInt() ;
            for( i = 0 ; i < testCases ; i++ ) {
                this.psObj.clearPerCase() ;
                this.psObj.getInput( this.irObj ) ;
                this.psObj.solveCase() ;
            }
        }
        else {
            while( true ) {
                this.psObj.clearPerCase() ;
                hasMoreTestCases = this.psObj.getInput( this.irObj ) ;
                if( hasMoreTestCases == false ) {
                    break;
                }
                this.psObj.solveCase() ;
            }
        }
        if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
            this.fohObj.flushOutOutputToFile( this.psObj.OUTPUT_FILE_NAME ) ;
        }
    } ;

    this.detectEnvironmentType = function() {
        var environmentType = null ;
        try {
            if( importPackage != null ) {
                environmentType = 'rhino' ;
            }
        }
        catch( ex1 ) {
            try {
                //for nodejs local server check
                if( __dirname != null && ( __dirname.indexOf( 'D:') != -1 || __dirname.indexOf( '/media/') != -1 ) ) {
                    environmentType = 'local-node-js' ;
                }
                else {
                    environmentType = 'server-node-js' ;
                }
            }
            catch( ex2 ) {
                try {
                    if( readline == null || typeof( readline ) != 'function' ) {
                        environmentType = 'server-node-js' ;
                    }
                    else {
                        try {
                            if( Map != null ) {
                                environmentType = 'spider-monkey' ;
                            }
                            else {
                                environmentType = 'javascript-v8' ;
                            }
                        }
                        catch( ex3 ) {
                            environmentType = 'javascript-v8' ;
                        }
                    }
                }
                catch( ex3 ) {
                    environmentType = 'server-node-js' ;
                }
            }
        }
        return environmentType ;
    } ;

    this.configureStreamsAndReadInput = function() {
        var localContext , isNodeJsJudgeServer , environmentType ;
        isNodeJsJudgeServer = false ;
        environmentType = this.detectEnvironmentType() ;
        if( environmentType == 'local-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
                localContext = this.fohObj ;
                print = function() {
                    localContext.addNewLine.apply( localContext , arguments ) ;
                }
            }
            this.irObj.readAllLinesFromFile( this.psObj.INPUT_FILE_NAME ) ;
            this.runCases() ;
        }
        else if( environmentType == 'server-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            this.irObj.readAllLinesFromNodeJsJudgeServer( this ) ;
        }
        else if( environmentType == 'javascript-v8' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
        else if( environmentType == 'rhino' ) {
            this.irObj.readAllLinesFromRhino() ;
            this.runCases() ;
        }
        else if( environmentType == 'spider-monkey' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
    } ;

    this.configureStreamsAndReadInput() ;
}

new CodeExecutioner() ;

function ProblemSolver() {
    this.HAS_TEST_CASES = false ;
    this.INPUT_FILE_NAME = "sample.in" ;
    this.OUTPUT_FILE_NAME = "sample.out" ;
    this.DO_OUTPUT_TO_FILE = false ;
    this.CLEAR_ARRAY_PER_CASE = false ;

    this.solveCase = function() {
        var res , i , j , fl , cn , a , b , c , lo , hi , mi , eps ;
        this.arr = this.arr.sort( function( le , ri ) { return le - ri ; } ) ;
        res = 0 ;
        lo = 0.0 ;
        hi = this.arr[ 0 ] * 1.0 ;
        eps = 1e-12 ;
        cn = 10000 ;
        while( ( hi - lo ) >= eps && cn-- > 0 ) {
            mi = ( lo + hi ) / 2.0 ;
            a = 2.0 * mi ;
            if( mi < this.arr[ 0 ] + eps && a < this.arr[ this.n ] + eps && mi + a < ( this.w / this.n ) + eps ) {
                lo = mi ;
                res = mi * this.n + a * this.n ;
            }
            else {
                hi = mi ;
            }
        }
        print( res.toFixed( 10 ) ) ;
    } ;

    this.init = function() {
        this.lim1 = 100010 ;
        this.lim2 = 110 ;
        this.cc = 1 ;
        this.ind = 1 ;
        this.n = 0 ;
        this.cn = 0 ;
        this.declareAndFillArrays() ;
    } ;

    this.getInput = function( irObj ) {
        var hasMoreInput , i ;
        hasMoreInput = true ;
        try {
        	this.n = irObj.nextInt() ;
        	this.w = irObj.nextInt() ;
            this.arr = [] ;
            for( i = 0 ; i < 2 * this.n ; i++ ) {
                this.arr.push( irObj.nextInt() ) ;
            }
        }
        catch( ex ) {
            hasMoreInput = false ;
        }
        return hasMoreInput ;
    } ;

    this.clearArraysPerCase = function() {
        var i ;
        this.arr = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.arr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
    } ;

    this.clearPerCase = function() {
        this.cn = 0 ;
        this.cc++ ;
        if( this.CLEAR_ARRAY_PER_CASE == true ) {
            this.clearArraysPerCase() ;
        }
    } ;

    this.declareAndFillArrays = function() {
        var i , j ;
        this.srr = new Array() ;
        this.vis = new Array() ;
        this.arr = new Array() ;
        this.brr = new Array() ;
        this.memo = new Array() ;
        this.done = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.srr.push( '' ) ;
            this.vis.push( 0 ) ;
            this.arr.push( 0 ) ;
            this.brr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
        for( i = 0 ; i < this.lim2 ; i++ ) {
            this.memo.push( new Array() ) ;
            this.done.push( new Array() ) ;
            for( j = 0 ; j < this.lim2 ; j++ ) {
                this.memo[ i ].push( -1 ) ;
                this.done[ i ].push( 0 ) ;
            }
        }
    } ;

    this.init() ;
}

function InputReader() {
    var self = this ;
    this.allLines = new Array() ;
    this.currrentLineNumber = 0 ;
    this.currrentCharacterIndex = 0 ;
    this.callBackFunction = null ;
    this.parentContext = null ;

    this.readAllLines = function() {
        var singleLine ;
        while( true ) {
            try {
                singleLine = readline() ;
                if( singleLine == null ) {
                    break ;
                }
            }
            catch( ex ) {
                break ;
            }
            this.allLines.push( singleLine ) ;
        }
    } ;

    this.readAllLinesFromRhino = function() {
        var brObj , line ;
        importPackage( java.io ) ;
        importPackage( java.lang ) ;
        brObj = new BufferedReader( new InputStreamReader( System[ 'in' ] ) ) ;
        this.allLines = [] ;
        while( true ) {
            line = brObj.readLine() ;
            if( line == null ) {
                break;
            }
            this.allLines.push( line ) ;
        }
    } ;

    this.readSingleLinesFromNodeJsJudgeServer = function( chunk ) {
        self.chunkData += chunk ;
    } ;

    this.readEndFromNodeJsJudgeServer = function() {
        self.parseRawData( self.chunkData ) ;
        self.parentContext.runCases() ;
    } ;

    this.readAllLinesFromNodeJsJudgeServer = function( parentContext ) {
        this.parentContext = parentContext ;
        process.stdin.resume() ;
        process.stdin.setEncoding( 'utf8' ) ;
        this.chunkData = '' ;
        process.stdin.on( 'data' , this.readSingleLinesFromNodeJsJudgeServer ) ;
        process.stdin.on( 'end' , this.readEndFromNodeJsJudgeServer ) ;
    } ;

    this.parseRawData = function( data ) {
        var len , i , currentString ;
        len = data.length ;
        currentString = '' ;
        this.allLines = [] ;
        for( i = 0 ; i < len ; i++ ) {
            if( data[ i ] == '\r' ) {
            }
            else if( data[ i ] == '\n' ) {
                this.allLines.push( currentString ) ;
                currentString = '' ;
            }
            else {
                currentString += data[ i ] ;
            }
        }
        if( currentString != '' ) {
            this.allLines.push( currentString ) ;
        }
    } ;

    this.readAllLinesFromFile = function( inputFileName ) {
        var currentDirectory , fsObj , inputFilePath , rawData ;
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            inputFilePath = currentDirectory + '\\' + inputFileName ;
        }
        else {
            //on linux
            inputFilePath = currentDirectory + '/' + inputFileName ;
        }
        rawData = fsObj.readFileSync( inputFilePath , "utf8" ) ;
        this.parseRawData( rawData ) ;
    } ;

    this.next = function( flag ) {
        var len , i , startIdx , res , endIdx ;
        if( flag == 0 ) {
            if( this.currrentCharacterIndex != 0 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            res = '' ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
            }
            this.currrentLineNumber++ ;
            this.currrentCharacterIndex = 0 ;
            return res ;
        }
        while( true ) {
            if( this.currrentLineNumber >= this.allLines.length ) {
                throw new Error( 'No more tokens available!' ) ;
            }
            startIdx = -1 ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) != ' '.charCodeAt( 0 ) ) {
                    startIdx = i ;
                    break ;
                }
            }
            if( startIdx == -1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
                continue ;
            }
            res = '' ;
            endIdx = len - 1 ;
            for( i = startIdx ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) == ' '.charCodeAt( 0 ) ) {
                    endIdx = i ;
                    break ;
                }
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) >= 48 && this.allLines[ this.currrentLineNumber ].charCodeAt( i ) <= 57 ) {
                    res += '' + ( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) - 48 ) ;
                }
                else {
                    res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
                }
            }
            this.currrentCharacterIndex = endIdx ;
            if( endIdx == len - 1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            return res ;
        }
    } ;

    this.nextInt = function() {
        return parseInt( this.next( 1 ) ) ;
    } ;

    this.nextDouble = function() {
        return parseFloat( this.next( 1 ) ) ;
    } ;

    this.nextString = function() {
        return this.next( 1 ) ;
    } ;

    this.nextLine = function() {
        return this.next( 0 ) ;
    } ;
}

function FileOutputHandler() {
    this.resultantStringArray = new Array() ;

    this.addNewLine = function( newString ) {
        this.resultantStringArray.push( newString ) ;
    } ;

    this.clearPercase = function() {
        this.resultantStringArray = new Array() ;
    } ;

    this.flushOutOutputToFile = function( outputFileName ) {
        var i , sz , res , currentDirectory , fsObj , outputFilePath ;
        res = '' ;
        sz = this.resultantStringArray.length ;
        for( i = 0 ; i < sz ; i++ ) {
            if( i != 0 ) {
                res += '\n' ;
            }
            res += this.resultantStringArray[ i ] ;
        }
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            outputFilePath = currentDirectory + '\\' + outputFileName ;
        }
        else {
            //on linux
            outputFilePath = currentDirectory + '/' + outputFileName ;
        }
        fsObj.writeFileSync( outputFilePath , res ) ;
        this.clearPercase() ;
    } ;
}

function CodeExecutioner() {
    this.irObj = new InputReader() ;
    this.psObj = new ProblemSolver() ;
    this.fohObj = new FileOutputHandler() ;

    this.runCases = function() {
		var testCases , hasMoreTestCases , i ;
        if( this.psObj.HAS_TEST_CASES == true ) {
            testCases = this.irObj.nextInt() ;
            for( i = 0 ; i < testCases ; i++ ) {
                this.psObj.clearPerCase() ;
                this.psObj.getInput( this.irObj ) ;
                this.psObj.solveCase() ;
            }
        }
        else {
            while( true ) {
                this.psObj.clearPerCase() ;
                hasMoreTestCases = this.psObj.getInput( this.irObj ) ;
                if( hasMoreTestCases == false ) {
                    break;
                }
                this.psObj.solveCase() ;
            }
        }
        if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
            this.fohObj.flushOutOutputToFile( this.psObj.OUTPUT_FILE_NAME ) ;
        }
    } ;

    this.detectEnvironmentType = function() {
        var environmentType = null ;
        try {
            if( importPackage != null ) {
                environmentType = 'rhino' ;
            }
        }
        catch( ex1 ) {
            try {
                //for nodejs local server check
                if( __dirname != null && ( __dirname.indexOf( 'D:') != -1 || __dirname.indexOf( '/media/') != -1 ) ) {
                    environmentType = 'local-node-js' ;
                }
                else {
                    environmentType = 'server-node-js' ;
                }
            }
            catch( ex2 ) {
                try {
                    if( readline == null || typeof( readline ) != 'function' ) {
                        environmentType = 'server-node-js' ;
                    }
                    else {
                        try {
                            if( Map != null ) {
                                environmentType = 'spider-monkey' ;
                            }
                            else {
                                environmentType = 'javascript-v8' ;
                            }
                        }
                        catch( ex3 ) {
                            environmentType = 'javascript-v8' ;
                        }
                    }
                }
                catch( ex3 ) {
                    environmentType = 'server-node-js' ;
                }
            }
        }
        return environmentType ;
    } ;

    this.configureStreamsAndReadInput = function() {
        var localContext , isNodeJsJudgeServer , environmentType ;
        isNodeJsJudgeServer = false ;
        environmentType = this.detectEnvironmentType() ;
        if( environmentType == 'local-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
                localContext = this.fohObj ;
                print = function() {
                    localContext.addNewLine.apply( localContext , arguments ) ;
                }
            }
            this.irObj.readAllLinesFromFile( this.psObj.INPUT_FILE_NAME ) ;
            this.runCases() ;
        }
        else if( environmentType == 'server-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            this.irObj.readAllLinesFromNodeJsJudgeServer( this ) ;
        }
        else if( environmentType == 'javascript-v8' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
        else if( environmentType == 'rhino' ) {
            this.irObj.readAllLinesFromRhino() ;
            this.runCases() ;
        }
        else if( environmentType == 'spider-monkey' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
    } ;

    this.configureStreamsAndReadInput() ;
}

new CodeExecutioner() ;

function ProblemSolver() {
    this.HAS_TEST_CASES = false ;
    this.INPUT_FILE_NAME = "sample.in" ;
    this.OUTPUT_FILE_NAME = "sample.out" ;
    this.DO_OUTPUT_TO_FILE = false ;
    this.CLEAR_ARRAY_PER_CASE = false ;

    this.solveCase = function() {
        var res , i , j , fl , cn , a , b , c , lo , hi , mi , eps ;
        this.arr = this.arr.sort( function( le , ri ) { return le - ri ; } ) ;
        res = 0 ;
        lo = 0.0 ;
        hi = this.arr[ 0 ] * 1.0 ;
        eps = 1e-11 ;
        cn = 100 ;
        while( ( hi - lo ) >= eps && cn-- > 0 ) {
            mi = ( lo + hi ) / 2.0 ;
            a = 2.0 * mi ;
            if( mi < this.arr[ 0 ] + eps && a < this.arr[ this.n ] + eps && mi * this.n + a * this.n < ( this.w ) + eps ) {
                lo = mi ;
                res = mi * this.n + a * this.n ;
            }
            else {
                hi = mi ;
            }
        }
        print( res.toFixed( 10 ) ) ;
    } ;

    this.init = function() {
        this.lim1 = 100010 ;
        this.lim2 = 110 ;
        this.cc = 1 ;
        this.ind = 1 ;
        this.n = 0 ;
        this.cn = 0 ;
        this.declareAndFillArrays() ;
    } ;

    this.getInput = function( irObj ) {
        var hasMoreInput , i ;
        hasMoreInput = true ;
        try {
        	this.n = irObj.nextInt() ;
        	this.w = irObj.nextInt() ;
            this.arr = [] ;
            for( i = 0 ; i < 2 * this.n ; i++ ) {
                this.arr.push( irObj.nextInt() ) ;
            }
        }
        catch( ex ) {
            hasMoreInput = false ;
        }
        return hasMoreInput ;
    } ;

    this.clearArraysPerCase = function() {
        var i ;
        this.arr = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.arr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
    } ;

    this.clearPerCase = function() {
        this.cn = 0 ;
        this.cc++ ;
        if( this.CLEAR_ARRAY_PER_CASE == true ) {
            this.clearArraysPerCase() ;
        }
    } ;

    this.declareAndFillArrays = function() {
        var i , j ;
        this.srr = new Array() ;
        this.vis = new Array() ;
        this.arr = new Array() ;
        this.brr = new Array() ;
        this.memo = new Array() ;
        this.done = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.srr.push( '' ) ;
            this.vis.push( 0 ) ;
            this.arr.push( 0 ) ;
            this.brr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
        for( i = 0 ; i < this.lim2 ; i++ ) {
            this.memo.push( new Array() ) ;
            this.done.push( new Array() ) ;
            for( j = 0 ; j < this.lim2 ; j++ ) {
                this.memo[ i ].push( -1 ) ;
                this.done[ i ].push( 0 ) ;
            }
        }
    } ;

    this.init() ;
}

function InputReader() {
    var self = this ;
    this.allLines = new Array() ;
    this.currrentLineNumber = 0 ;
    this.currrentCharacterIndex = 0 ;
    this.callBackFunction = null ;
    this.parentContext = null ;

    this.readAllLines = function() {
        var singleLine ;
        while( true ) {
            try {
                singleLine = readline() ;
                if( singleLine == null ) {
                    break ;
                }
            }
            catch( ex ) {
                break ;
            }
            this.allLines.push( singleLine ) ;
        }
    } ;

    this.readAllLinesFromRhino = function() {
        var brObj , line ;
        importPackage( java.io ) ;
        importPackage( java.lang ) ;
        brObj = new BufferedReader( new InputStreamReader( System[ 'in' ] ) ) ;
        this.allLines = [] ;
        while( true ) {
            line = brObj.readLine() ;
            if( line == null ) {
                break;
            }
            this.allLines.push( line ) ;
        }
    } ;

    this.readSingleLinesFromNodeJsJudgeServer = function( chunk ) {
        self.chunkData += chunk ;
    } ;

    this.readEndFromNodeJsJudgeServer = function() {
        self.parseRawData( self.chunkData ) ;
        self.parentContext.runCases() ;
    } ;

    this.readAllLinesFromNodeJsJudgeServer = function( parentContext ) {
        this.parentContext = parentContext ;
        process.stdin.resume() ;
        process.stdin.setEncoding( 'utf8' ) ;
        this.chunkData = '' ;
        process.stdin.on( 'data' , this.readSingleLinesFromNodeJsJudgeServer ) ;
        process.stdin.on( 'end' , this.readEndFromNodeJsJudgeServer ) ;
    } ;

    this.parseRawData = function( data ) {
        var len , i , currentString ;
        len = data.length ;
        currentString = '' ;
        this.allLines = [] ;
        for( i = 0 ; i < len ; i++ ) {
            if( data[ i ] == '\r' ) {
            }
            else if( data[ i ] == '\n' ) {
                this.allLines.push( currentString ) ;
                currentString = '' ;
            }
            else {
                currentString += data[ i ] ;
            }
        }
        if( currentString != '' ) {
            this.allLines.push( currentString ) ;
        }
    } ;

    this.readAllLinesFromFile = function( inputFileName ) {
        var currentDirectory , fsObj , inputFilePath , rawData ;
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            inputFilePath = currentDirectory + '\\' + inputFileName ;
        }
        else {
            //on linux
            inputFilePath = currentDirectory + '/' + inputFileName ;
        }
        rawData = fsObj.readFileSync( inputFilePath , "utf8" ) ;
        this.parseRawData( rawData ) ;
    } ;

    this.next = function( flag ) {
        var len , i , startIdx , res , endIdx ;
        if( flag == 0 ) {
            if( this.currrentCharacterIndex != 0 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            res = '' ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
            }
            this.currrentLineNumber++ ;
            this.currrentCharacterIndex = 0 ;
            return res ;
        }
        while( true ) {
            if( this.currrentLineNumber >= this.allLines.length ) {
                throw new Error( 'No more tokens available!' ) ;
            }
            startIdx = -1 ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) != ' '.charCodeAt( 0 ) ) {
                    startIdx = i ;
                    break ;
                }
            }
            if( startIdx == -1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
                continue ;
            }
            res = '' ;
            endIdx = len - 1 ;
            for( i = startIdx ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) == ' '.charCodeAt( 0 ) ) {
                    endIdx = i ;
                    break ;
                }
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) >= 48 && this.allLines[ this.currrentLineNumber ].charCodeAt( i ) <= 57 ) {
                    res += '' + ( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) - 48 ) ;
                }
                else {
                    res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
                }
            }
            this.currrentCharacterIndex = endIdx ;
            if( endIdx == len - 1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            return res ;
        }
    } ;

    this.nextInt = function() {
        return parseInt( this.next( 1 ) ) ;
    } ;

    this.nextDouble = function() {
        return parseFloat( this.next( 1 ) ) ;
    } ;

    this.nextString = function() {
        return this.next( 1 ) ;
    } ;

    this.nextLine = function() {
        return this.next( 0 ) ;
    } ;
}

function FileOutputHandler() {
    this.resultantStringArray = new Array() ;

    this.addNewLine = function( newString ) {
        this.resultantStringArray.push( newString ) ;
    } ;

    this.clearPercase = function() {
        this.resultantStringArray = new Array() ;
    } ;

    this.flushOutOutputToFile = function( outputFileName ) {
        var i , sz , res , currentDirectory , fsObj , outputFilePath ;
        res = '' ;
        sz = this.resultantStringArray.length ;
        for( i = 0 ; i < sz ; i++ ) {
            if( i != 0 ) {
                res += '\n' ;
            }
            res += this.resultantStringArray[ i ] ;
        }
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            outputFilePath = currentDirectory + '\\' + outputFileName ;
        }
        else {
            //on linux
            outputFilePath = currentDirectory + '/' + outputFileName ;
        }
        fsObj.writeFileSync( outputFilePath , res ) ;
        this.clearPercase() ;
    } ;
}

function CodeExecutioner() {
    this.irObj = new InputReader() ;
    this.psObj = new ProblemSolver() ;
    this.fohObj = new FileOutputHandler() ;

    this.runCases = function() {
		var testCases , hasMoreTestCases , i ;
        if( this.psObj.HAS_TEST_CASES == true ) {
            testCases = this.irObj.nextInt() ;
            for( i = 0 ; i < testCases ; i++ ) {
                this.psObj.clearPerCase() ;
                this.psObj.getInput( this.irObj ) ;
                this.psObj.solveCase() ;
            }
        }
        else {
            while( true ) {
                this.psObj.clearPerCase() ;
                hasMoreTestCases = this.psObj.getInput( this.irObj ) ;
                if( hasMoreTestCases == false ) {
                    break;
                }
                this.psObj.solveCase() ;
            }
        }
        if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
            this.fohObj.flushOutOutputToFile( this.psObj.OUTPUT_FILE_NAME ) ;
        }
    } ;

    this.detectEnvironmentType = function() {
        var environmentType = null ;
        try {
            if( importPackage != null ) {
                environmentType = 'rhino' ;
            }
        }
        catch( ex1 ) {
            try {
                //for nodejs local server check
                if( __dirname != null && ( __dirname.indexOf( 'D:') != -1 || __dirname.indexOf( '/media/') != -1 ) ) {
                    environmentType = 'local-node-js' ;
                }
                else {
                    environmentType = 'server-node-js' ;
                }
            }
            catch( ex2 ) {
                try {
                    if( readline == null || typeof( readline ) != 'function' ) {
                        environmentType = 'server-node-js' ;
                    }
                    else {
                        try {
                            if( Map != null ) {
                                environmentType = 'spider-monkey' ;
                            }
                            else {
                                environmentType = 'javascript-v8' ;
                            }
                        }
                        catch( ex3 ) {
                            environmentType = 'javascript-v8' ;
                        }
                    }
                }
                catch( ex3 ) {
                    environmentType = 'server-node-js' ;
                }
            }
        }
        return environmentType ;
    } ;

    this.configureStreamsAndReadInput = function() {
        var localContext , isNodeJsJudgeServer , environmentType ;
        isNodeJsJudgeServer = false ;
        environmentType = this.detectEnvironmentType() ;
        if( environmentType == 'local-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
                localContext = this.fohObj ;
                print = function() {
                    localContext.addNewLine.apply( localContext , arguments ) ;
                }
            }
            this.irObj.readAllLinesFromFile( this.psObj.INPUT_FILE_NAME ) ;
            this.runCases() ;
        }
        else if( environmentType == 'server-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            this.irObj.readAllLinesFromNodeJsJudgeServer( this ) ;
        }
        else if( environmentType == 'javascript-v8' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
        else if( environmentType == 'rhino' ) {
            this.irObj.readAllLinesFromRhino() ;
            this.runCases() ;
        }
        else if( environmentType == 'spider-monkey' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
    } ;

    this.configureStreamsAndReadInput() ;
}

new CodeExecutioner() ;

'use strict';

process.stdin.resume();
process.stdin.setEncoding('utf-8');

let inputString = '';
let currentLine = 0;

process.stdin.on('data', inputStdin => {
    inputString += inputStdin;
});

process.stdin.on('end', _ => {
    inputString = inputString.trim().split('\n').map(string => {
        return string.trim();
    });

    main();
});

function readLine() {
    return inputString[currentLine++];
}

function printResult(x) {
    process.stdout.write(x);
}

function main() {
    const nw = readLine().split(' ').map(Number);
    const arr = readLine().split(' ').map(Number);

    const result = pashaAndTea(nw[0], nw[1], arr);
    printResult(result.toString());
}

const compare = (a, b) => a - b;

const pashaAndTea = (n, w, a) => {
    a.sort(compare);
    if (w === 1) return w;
    const x = Math.min(a[0], a[n]/2)

    return Math.min(w, x*n*3)
};

'use strict';

process.stdin.resume();
process.stdin.setEncoding('utf-8');

let inputString = '';
let currentLine = 0;

process.stdin.on('data', inputStdin => {
    inputString += inputStdin;
});

process.stdin.on('end', _ => {
    inputString = inputString.trim().split('\n').map(string => {
        return string.trim();
    });

    main();
});

function readLine() {
    return inputString[currentLine++];
}

function printResult(x) {
    process.stdout.write(x);
}

function main() {
    const nw = readLine().split(' ').map(Number);
    const arr = readLine().split(' ').map(Number);

    const result = pashaAndTea(nw[0], nw[1], arr);
    printResult(result.toString());
}

const compare = (a, b) => b - a;

const pashaAndTea = (n, w, a) => {
    a.sort(compare);
    if (w === 1) return w;
    // Max amount of water to each boy: 2w/3n;
    let boyWater = a[n - 1];
    if ((boyWater * 3 * n) / 2 > w) {
        boyWater = (2 * w) / (3 * n);
    }
    let girlWater = a[2*n - 1];
    if (girlWater >= boyWater / 2) girlWater = boyWater / 2;

    return (girlWater * n) + (girlWater * 2 * n);
};

function ProblemSolver() {
    this.HAS_TEST_CASES = false ;
    this.INPUT_FILE_NAME = "sample.in" ;
    this.OUTPUT_FILE_NAME = "sample.out" ;
    this.DO_OUTPUT_TO_FILE = false ;
    this.CLEAR_ARRAY_PER_CASE = false ;

    this.solveCase = function() {
        var res , i , j , fl , cn , a , b , c , lo , hi , mi , eps ;
        this.arr = this.arr.sort( function( le , ri ) { return le - ri ; } ) ;
        res = 0 ;
        lo = 0.0 ;
        hi = this.arr[ 0 ] * 1.0 ;
        eps = 1e-9 ;
        cn = 10000 ;
        while( ( hi - lo ) >= eps && cn-- > 0 ) {
            mi = ( lo + hi ) / 2.0 ;
            a = 2.0 * mi ;
            if( mi < this.arr[ 0 ] + eps && a < this.arr[ this.n ] + eps && mi * this.n < this.w + eps && a * this.n < this.w + eps && mi * this.n + a * this.n < this.w + eps ) {
                lo = mi ;
                res = mi * this.n + a * this.n ;
            }
            else {
                hi = mi ;
            }
        }
        print( res.toFixed( 10 ) ) ;
    } ;

    this.init = function() {
        this.lim1 = 100010 ;
        this.lim2 = 110 ;
        this.cc = 1 ;
        this.ind = 1 ;
        this.n = 0 ;
        this.cn = 0 ;
        this.declareAndFillArrays() ;
    } ;

    this.getInput = function( irObj ) {
        var hasMoreInput , i ;
        hasMoreInput = true ;
        try {
        	this.n = irObj.nextInt() ;
        	this.w = irObj.nextInt() ;
            this.arr = [] ;
            for( i = 0 ; i < 2 * this.n ; i++ ) {
                this.arr.push( irObj.nextInt() ) ;
            }
        }
        catch( ex ) {
            hasMoreInput = false ;
        }
        return hasMoreInput ;
    } ;

    this.clearArraysPerCase = function() {
        var i ;
        this.arr = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.arr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
    } ;

    this.clearPerCase = function() {
        this.cn = 0 ;
        this.cc++ ;
        if( this.CLEAR_ARRAY_PER_CASE == true ) {
            this.clearArraysPerCase() ;
        }
    } ;

    this.declareAndFillArrays = function() {
        var i , j ;
        this.srr = new Array() ;
        this.vis = new Array() ;
        this.arr = new Array() ;
        this.brr = new Array() ;
        this.memo = new Array() ;
        this.done = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.srr.push( '' ) ;
            this.vis.push( 0 ) ;
            this.arr.push( 0 ) ;
            this.brr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
        for( i = 0 ; i < this.lim2 ; i++ ) {
            this.memo.push( new Array() ) ;
            this.done.push( new Array() ) ;
            for( j = 0 ; j < this.lim2 ; j++ ) {
                this.memo[ i ].push( -1 ) ;
                this.done[ i ].push( 0 ) ;
            }
        }
    } ;

    this.init() ;
}

function InputReader() {
    var self = this ;
    this.allLines = new Array() ;
    this.currrentLineNumber = 0 ;
    this.currrentCharacterIndex = 0 ;
    this.callBackFunction = null ;
    this.parentContext = null ;

    this.readAllLines = function() {
        var singleLine ;
        while( true ) {
            try {
                singleLine = readline() ;
                if( singleLine == null ) {
                    break ;
                }
            }
            catch( ex ) {
                break ;
            }
            this.allLines.push( singleLine ) ;
        }
    } ;

    this.readAllLinesFromRhino = function() {
        var brObj , line ;
        importPackage( java.io ) ;
        importPackage( java.lang ) ;
        brObj = new BufferedReader( new InputStreamReader( System[ 'in' ] ) ) ;
        this.allLines = [] ;
        while( true ) {
            line = brObj.readLine() ;
            if( line == null ) {
                break;
            }
            this.allLines.push( line ) ;
        }
    } ;

    this.readSingleLinesFromNodeJsJudgeServer = function( chunk ) {
        self.chunkData += chunk ;
    } ;

    this.readEndFromNodeJsJudgeServer = function() {
        self.parseRawData( self.chunkData ) ;
        self.parentContext.runCases() ;
    } ;

    this.readAllLinesFromNodeJsJudgeServer = function( parentContext ) {
        this.parentContext = parentContext ;
        process.stdin.resume() ;
        process.stdin.setEncoding( 'utf8' ) ;
        this.chunkData = '' ;
        process.stdin.on( 'data' , this.readSingleLinesFromNodeJsJudgeServer ) ;
        process.stdin.on( 'end' , this.readEndFromNodeJsJudgeServer ) ;
    } ;

    this.parseRawData = function( data ) {
        var len , i , currentString ;
        len = data.length ;
        currentString = '' ;
        this.allLines = [] ;
        for( i = 0 ; i < len ; i++ ) {
            if( data[ i ] == '\r' ) {
            }
            else if( data[ i ] == '\n' ) {
                this.allLines.push( currentString ) ;
                currentString = '' ;
            }
            else {
                currentString += data[ i ] ;
            }
        }
        if( currentString != '' ) {
            this.allLines.push( currentString ) ;
        }
    } ;

    this.readAllLinesFromFile = function( inputFileName ) {
        var currentDirectory , fsObj , inputFilePath , rawData ;
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            inputFilePath = currentDirectory + '\\' + inputFileName ;
        }
        else {
            //on linux
            inputFilePath = currentDirectory + '/' + inputFileName ;
        }
        rawData = fsObj.readFileSync( inputFilePath , "utf8" ) ;
        this.parseRawData( rawData ) ;
    } ;

    this.next = function( flag ) {
        var len , i , startIdx , res , endIdx ;
        if( flag == 0 ) {
            if( this.currrentCharacterIndex != 0 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            res = '' ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
            }
            this.currrentLineNumber++ ;
            this.currrentCharacterIndex = 0 ;
            return res ;
        }
        while( true ) {
            if( this.currrentLineNumber >= this.allLines.length ) {
                throw new Error( 'No more tokens available!' ) ;
            }
            startIdx = -1 ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) != ' '.charCodeAt( 0 ) ) {
                    startIdx = i ;
                    break ;
                }
            }
            if( startIdx == -1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
                continue ;
            }
            res = '' ;
            endIdx = len - 1 ;
            for( i = startIdx ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) == ' '.charCodeAt( 0 ) ) {
                    endIdx = i ;
                    break ;
                }
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) >= 48 && this.allLines[ this.currrentLineNumber ].charCodeAt( i ) <= 57 ) {
                    res += '' + ( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) - 48 ) ;
                }
                else {
                    res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
                }
            }
            this.currrentCharacterIndex = endIdx ;
            if( endIdx == len - 1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            return res ;
        }
    } ;

    this.nextInt = function() {
        return parseInt( this.next( 1 ) ) ;
    } ;

    this.nextDouble = function() {
        return parseFloat( this.next( 1 ) ) ;
    } ;

    this.nextString = function() {
        return this.next( 1 ) ;
    } ;

    this.nextLine = function() {
        return this.next( 0 ) ;
    } ;
}

function FileOutputHandler() {
    this.resultantStringArray = new Array() ;

    this.addNewLine = function( newString ) {
        this.resultantStringArray.push( newString ) ;
    } ;

    this.clearPercase = function() {
        this.resultantStringArray = new Array() ;
    } ;

    this.flushOutOutputToFile = function( outputFileName ) {
        var i , sz , res , currentDirectory , fsObj , outputFilePath ;
        res = '' ;
        sz = this.resultantStringArray.length ;
        for( i = 0 ; i < sz ; i++ ) {
            if( i != 0 ) {
                res += '\n' ;
            }
            res += this.resultantStringArray[ i ] ;
        }
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            outputFilePath = currentDirectory + '\\' + outputFileName ;
        }
        else {
            //on linux
            outputFilePath = currentDirectory + '/' + outputFileName ;
        }
        fsObj.writeFileSync( outputFilePath , res ) ;
        this.clearPercase() ;
    } ;
}

function CodeExecutioner() {
    this.irObj = new InputReader() ;
    this.psObj = new ProblemSolver() ;
    this.fohObj = new FileOutputHandler() ;

    this.runCases = function() {
		var testCases , hasMoreTestCases , i ;
        if( this.psObj.HAS_TEST_CASES == true ) {
            testCases = this.irObj.nextInt() ;
            for( i = 0 ; i < testCases ; i++ ) {
                this.psObj.clearPerCase() ;
                this.psObj.getInput( this.irObj ) ;
                this.psObj.solveCase() ;
            }
        }
        else {
            while( true ) {
                this.psObj.clearPerCase() ;
                hasMoreTestCases = this.psObj.getInput( this.irObj ) ;
                if( hasMoreTestCases == false ) {
                    break;
                }
                this.psObj.solveCase() ;
            }
        }
        if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
            this.fohObj.flushOutOutputToFile( this.psObj.OUTPUT_FILE_NAME ) ;
        }
    } ;

    this.detectEnvironmentType = function() {
        var environmentType = null ;
        try {
            if( importPackage != null ) {
                environmentType = 'rhino' ;
            }
        }
        catch( ex1 ) {
            try {
                //for nodejs local server check
                if( __dirname != null && ( __dirname.indexOf( 'D:') != -1 || __dirname.indexOf( '/media/') != -1 ) ) {
                    environmentType = 'local-node-js' ;
                }
                else {
                    environmentType = 'server-node-js' ;
                }
            }
            catch( ex2 ) {
                try {
                    if( readline == null || typeof( readline ) != 'function' ) {
                        environmentType = 'server-node-js' ;
                    }
                    else {
                        try {
                            if( Map != null ) {
                                environmentType = 'spider-monkey' ;
                            }
                            else {
                                environmentType = 'javascript-v8' ;
                            }
                        }
                        catch( ex3 ) {
                            environmentType = 'javascript-v8' ;
                        }
                    }
                }
                catch( ex3 ) {
                    environmentType = 'server-node-js' ;
                }
            }
        }
        return environmentType ;
    } ;

    this.configureStreamsAndReadInput = function() {
        var localContext , isNodeJsJudgeServer , environmentType ;
        isNodeJsJudgeServer = false ;
        environmentType = this.detectEnvironmentType() ;
        if( environmentType == 'local-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
                localContext = this.fohObj ;
                print = function() {
                    localContext.addNewLine.apply( localContext , arguments ) ;
                }
            }
            this.irObj.readAllLinesFromFile( this.psObj.INPUT_FILE_NAME ) ;
            this.runCases() ;
        }
        else if( environmentType == 'server-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            this.irObj.readAllLinesFromNodeJsJudgeServer( this ) ;
        }
        else if( environmentType == 'javascript-v8' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
        else if( environmentType == 'rhino' ) {
            this.irObj.readAllLinesFromRhino() ;
            this.runCases() ;
        }
        else if( environmentType == 'spider-monkey' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
    } ;

    this.configureStreamsAndReadInput() ;
}

new CodeExecutioner() ;

function ProblemSolver() {
    this.HAS_TEST_CASES = false ;
    this.INPUT_FILE_NAME = "sample.in" ;
    this.OUTPUT_FILE_NAME = "sample.out" ;
    this.DO_OUTPUT_TO_FILE = false ;
    this.CLEAR_ARRAY_PER_CASE = false ;

    this.solveCase = function() {
        var res , i , j , fl , cn , a , b , c , lo , hi , mi , eps ;
        this.arr = this.arr.sort( function( le , ri ) { return le - ri ; } ) ;
        res = 0 ;
        lo = 0.0 ;
        hi = this.arr[ 0 ] * 1.0 ;
        eps = 1e-9 ;
        cn = 100 ;
        while( ( hi - lo ) >= eps && cn-- > 0 ) {
            mi = ( lo + hi ) / 2.0 ;
            a = 2.0 * mi ;
            if( mi < this.arr[ 0 ] + eps && a < this.arr[ this.n ] + eps ) {
                lo = mi ;
                res = mi * this.n + a * this.n ;
            }
            else {
                hi = mi ;
            }
        }
        print( res.toFixed( 10 ) ) ;
    } ;

    this.init = function() {
        this.lim1 = 100010 ;
        this.lim2 = 110 ;
        this.cc = 1 ;
        this.ind = 1 ;
        this.n = 0 ;
        this.cn = 0 ;
        this.declareAndFillArrays() ;
    } ;

    this.getInput = function( irObj ) {
        var hasMoreInput , i ;
        hasMoreInput = true ;
        try {
        	this.n = irObj.nextInt() ;
        	this.w = irObj.nextInt() ;
            this.arr = [] ;
            for( i = 0 ; i < 2 * this.n ; i++ ) {
                this.arr.push( irObj.nextInt() ) ;
            }
        }
        catch( ex ) {
            hasMoreInput = false ;
        }
        return hasMoreInput ;
    } ;

    this.clearArraysPerCase = function() {
        var i ;
        this.arr = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.arr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
    } ;

    this.clearPerCase = function() {
        this.cn = 0 ;
        this.cc++ ;
        if( this.CLEAR_ARRAY_PER_CASE == true ) {
            this.clearArraysPerCase() ;
        }
    } ;

    this.declareAndFillArrays = function() {
        var i , j ;
        this.srr = new Array() ;
        this.vis = new Array() ;
        this.arr = new Array() ;
        this.brr = new Array() ;
        this.memo = new Array() ;
        this.done = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.srr.push( '' ) ;
            this.vis.push( 0 ) ;
            this.arr.push( 0 ) ;
            this.brr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
        for( i = 0 ; i < this.lim2 ; i++ ) {
            this.memo.push( new Array() ) ;
            this.done.push( new Array() ) ;
            for( j = 0 ; j < this.lim2 ; j++ ) {
                this.memo[ i ].push( -1 ) ;
                this.done[ i ].push( 0 ) ;
            }
        }
    } ;

    this.init() ;
}

function InputReader() {
    var self = this ;
    this.allLines = new Array() ;
    this.currrentLineNumber = 0 ;
    this.currrentCharacterIndex = 0 ;
    this.callBackFunction = null ;
    this.parentContext = null ;

    this.readAllLines = function() {
        var singleLine ;
        while( true ) {
            try {
                singleLine = readline() ;
                if( singleLine == null ) {
                    break ;
                }
            }
            catch( ex ) {
                break ;
            }
            this.allLines.push( singleLine ) ;
        }
    } ;

    this.readAllLinesFromRhino = function() {
        var brObj , line ;
        importPackage( java.io ) ;
        importPackage( java.lang ) ;
        brObj = new BufferedReader( new InputStreamReader( System[ 'in' ] ) ) ;
        this.allLines = [] ;
        while( true ) {
            line = brObj.readLine() ;
            if( line == null ) {
                break;
            }
            this.allLines.push( line ) ;
        }
    } ;

    this.readSingleLinesFromNodeJsJudgeServer = function( chunk ) {
        self.chunkData += chunk ;
    } ;

    this.readEndFromNodeJsJudgeServer = function() {
        self.parseRawData( self.chunkData ) ;
        self.parentContext.runCases() ;
    } ;

    this.readAllLinesFromNodeJsJudgeServer = function( parentContext ) {
        this.parentContext = parentContext ;
        process.stdin.resume() ;
        process.stdin.setEncoding( 'utf8' ) ;
        this.chunkData = '' ;
        process.stdin.on( 'data' , this.readSingleLinesFromNodeJsJudgeServer ) ;
        process.stdin.on( 'end' , this.readEndFromNodeJsJudgeServer ) ;
    } ;

    this.parseRawData = function( data ) {
        var len , i , currentString ;
        len = data.length ;
        currentString = '' ;
        this.allLines = [] ;
        for( i = 0 ; i < len ; i++ ) {
            if( data[ i ] == '\r' ) {
            }
            else if( data[ i ] == '\n' ) {
                this.allLines.push( currentString ) ;
                currentString = '' ;
            }
            else {
                currentString += data[ i ] ;
            }
        }
        if( currentString != '' ) {
            this.allLines.push( currentString ) ;
        }
    } ;

    this.readAllLinesFromFile = function( inputFileName ) {
        var currentDirectory , fsObj , inputFilePath , rawData ;
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            inputFilePath = currentDirectory + '\\' + inputFileName ;
        }
        else {
            //on linux
            inputFilePath = currentDirectory + '/' + inputFileName ;
        }
        rawData = fsObj.readFileSync( inputFilePath , "utf8" ) ;
        this.parseRawData( rawData ) ;
    } ;

    this.next = function( flag ) {
        var len , i , startIdx , res , endIdx ;
        if( flag == 0 ) {
            if( this.currrentCharacterIndex != 0 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            res = '' ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
            }
            this.currrentLineNumber++ ;
            this.currrentCharacterIndex = 0 ;
            return res ;
        }
        while( true ) {
            if( this.currrentLineNumber >= this.allLines.length ) {
                throw new Error( 'No more tokens available!' ) ;
            }
            startIdx = -1 ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) != ' '.charCodeAt( 0 ) ) {
                    startIdx = i ;
                    break ;
                }
            }
            if( startIdx == -1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
                continue ;
            }
            res = '' ;
            endIdx = len - 1 ;
            for( i = startIdx ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) == ' '.charCodeAt( 0 ) ) {
                    endIdx = i ;
                    break ;
                }
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) >= 48 && this.allLines[ this.currrentLineNumber ].charCodeAt( i ) <= 57 ) {
                    res += '' + ( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) - 48 ) ;
                }
                else {
                    res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
                }
            }
            this.currrentCharacterIndex = endIdx ;
            if( endIdx == len - 1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            return res ;
        }
    } ;

    this.nextInt = function() {
        return parseInt( this.next( 1 ) ) ;
    } ;

    this.nextDouble = function() {
        return parseFloat( this.next( 1 ) ) ;
    } ;

    this.nextString = function() {
        return this.next( 1 ) ;
    } ;

    this.nextLine = function() {
        return this.next( 0 ) ;
    } ;
}

function FileOutputHandler() {
    this.resultantStringArray = new Array() ;

    this.addNewLine = function( newString ) {
        this.resultantStringArray.push( newString ) ;
    } ;

    this.clearPercase = function() {
        this.resultantStringArray = new Array() ;
    } ;

    this.flushOutOutputToFile = function( outputFileName ) {
        var i , sz , res , currentDirectory , fsObj , outputFilePath ;
        res = '' ;
        sz = this.resultantStringArray.length ;
        for( i = 0 ; i < sz ; i++ ) {
            if( i != 0 ) {
                res += '\n' ;
            }
            res += this.resultantStringArray[ i ] ;
        }
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            outputFilePath = currentDirectory + '\\' + outputFileName ;
        }
        else {
            //on linux
            outputFilePath = currentDirectory + '/' + outputFileName ;
        }
        fsObj.writeFileSync( outputFilePath , res ) ;
        this.clearPercase() ;
    } ;
}

function CodeExecutioner() {
    this.irObj = new InputReader() ;
    this.psObj = new ProblemSolver() ;
    this.fohObj = new FileOutputHandler() ;

    this.runCases = function() {
		var testCases , hasMoreTestCases , i ;
        if( this.psObj.HAS_TEST_CASES == true ) {
            testCases = this.irObj.nextInt() ;
            for( i = 0 ; i < testCases ; i++ ) {
                this.psObj.clearPerCase() ;
                this.psObj.getInput( this.irObj ) ;
                this.psObj.solveCase() ;
            }
        }
        else {
            while( true ) {
                this.psObj.clearPerCase() ;
                hasMoreTestCases = this.psObj.getInput( this.irObj ) ;
                if( hasMoreTestCases == false ) {
                    break;
                }
                this.psObj.solveCase() ;
            }
        }
        if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
            this.fohObj.flushOutOutputToFile( this.psObj.OUTPUT_FILE_NAME ) ;
        }
    } ;

    this.detectEnvironmentType = function() {
        var environmentType = null ;
        try {
            if( importPackage != null ) {
                environmentType = 'rhino' ;
            }
        }
        catch( ex1 ) {
            try {
                //for nodejs local server check
                if( __dirname != null && ( __dirname.indexOf( 'D:') != -1 || __dirname.indexOf( '/media/') != -1 ) ) {
                    environmentType = 'local-node-js' ;
                }
                else {
                    environmentType = 'server-node-js' ;
                }
            }
            catch( ex2 ) {
                try {
                    if( readline == null || typeof( readline ) != 'function' ) {
                        environmentType = 'server-node-js' ;
                    }
                    else {
                        try {
                            if( Map != null ) {
                                environmentType = 'spider-monkey' ;
                            }
                            else {
                                environmentType = 'javascript-v8' ;
                            }
                        }
                        catch( ex3 ) {
                            environmentType = 'javascript-v8' ;
                        }
                    }
                }
                catch( ex3 ) {
                    environmentType = 'server-node-js' ;
                }
            }
        }
        return environmentType ;
    } ;

    this.configureStreamsAndReadInput = function() {
        var localContext , isNodeJsJudgeServer , environmentType ;
        isNodeJsJudgeServer = false ;
        environmentType = this.detectEnvironmentType() ;
        if( environmentType == 'local-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
                localContext = this.fohObj ;
                print = function() {
                    localContext.addNewLine.apply( localContext , arguments ) ;
                }
            }
            this.irObj.readAllLinesFromFile( this.psObj.INPUT_FILE_NAME ) ;
            this.runCases() ;
        }
        else if( environmentType == 'server-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            this.irObj.readAllLinesFromNodeJsJudgeServer( this ) ;
        }
        else if( environmentType == 'javascript-v8' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
        else if( environmentType == 'rhino' ) {
            this.irObj.readAllLinesFromRhino() ;
            this.runCases() ;
        }
        else if( environmentType == 'spider-monkey' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
    } ;

    this.configureStreamsAndReadInput() ;
}

new CodeExecutioner() ;

function ProblemSolver() {
    this.HAS_TEST_CASES = false ;
    this.INPUT_FILE_NAME = "sample.in" ;
    this.OUTPUT_FILE_NAME = "sample.out" ;
    this.DO_OUTPUT_TO_FILE = false ;
    this.CLEAR_ARRAY_PER_CASE = false ;

    this.solveCase = function() {
        var res , i , j , fl , cn , a , b , c , lo , hi , mi , eps ;
        this.arr = this.arr.sort( function( le , ri ) { return le - ri ; } ) ;
        res = 0 ;
        lo = 0.0 ;
        hi = this.arr[ 0 ] * 1.0 ;
        eps = 1e-9 ;
        cn = 10000 ;
        while( ( hi - lo ) >= eps && cn-- > 0 ) {
            mi = ( lo + hi ) / 2.0 ;
            a = 2.0 * mi ;
            if( mi < this.arr[ 0 ] + eps && a < this.arr[ this.n ] + eps && mi * this.n + a * this.n < this.w + eps ) {
                lo = mi ;
                res = mi * this.n + a * this.n ;
            }
            else {
                hi = mi ;
            }
        }
        print( res.toFixed( 10 ) ) ;
    } ;

    this.init = function() {
        this.lim1 = 100010 ;
        this.lim2 = 110 ;
        this.cc = 1 ;
        this.ind = 1 ;
        this.n = 0 ;
        this.cn = 0 ;
        this.declareAndFillArrays() ;
    } ;

    this.getInput = function( irObj ) {
        var hasMoreInput , i ;
        hasMoreInput = true ;
        try {
        	this.n = irObj.nextInt() ;
        	this.w = irObj.nextInt() ;
            this.arr = [] ;
            for( i = 0 ; i < 2 * this.n ; i++ ) {
                this.arr.push( irObj.nextInt() ) ;
            }
        }
        catch( ex ) {
            hasMoreInput = false ;
        }
        return hasMoreInput ;
    } ;

    this.clearArraysPerCase = function() {
        var i ;
        this.arr = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.arr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
    } ;

    this.clearPerCase = function() {
        this.cn = 0 ;
        this.cc++ ;
        if( this.CLEAR_ARRAY_PER_CASE == true ) {
            this.clearArraysPerCase() ;
        }
    } ;

    this.declareAndFillArrays = function() {
        var i , j ;
        this.srr = new Array() ;
        this.vis = new Array() ;
        this.arr = new Array() ;
        this.brr = new Array() ;
        this.memo = new Array() ;
        this.done = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.srr.push( '' ) ;
            this.vis.push( 0 ) ;
            this.arr.push( 0 ) ;
            this.brr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
        for( i = 0 ; i < this.lim2 ; i++ ) {
            this.memo.push( new Array() ) ;
            this.done.push( new Array() ) ;
            for( j = 0 ; j < this.lim2 ; j++ ) {
                this.memo[ i ].push( -1 ) ;
                this.done[ i ].push( 0 ) ;
            }
        }
    } ;

    this.init() ;
}

function InputReader() {
    var self = this ;
    this.allLines = new Array() ;
    this.currrentLineNumber = 0 ;
    this.currrentCharacterIndex = 0 ;
    this.callBackFunction = null ;
    this.parentContext = null ;

    this.readAllLines = function() {
        var singleLine ;
        while( true ) {
            try {
                singleLine = readline() ;
                if( singleLine == null ) {
                    break ;
                }
            }
            catch( ex ) {
                break ;
            }
            this.allLines.push( singleLine ) ;
        }
    } ;

    this.readAllLinesFromRhino = function() {
        var brObj , line ;
        importPackage( java.io ) ;
        importPackage( java.lang ) ;
        brObj = new BufferedReader( new InputStreamReader( System[ 'in' ] ) ) ;
        this.allLines = [] ;
        while( true ) {
            line = brObj.readLine() ;
            if( line == null ) {
                break;
            }
            this.allLines.push( line ) ;
        }
    } ;

    this.readSingleLinesFromNodeJsJudgeServer = function( chunk ) {
        self.chunkData += chunk ;
    } ;

    this.readEndFromNodeJsJudgeServer = function() {
        self.parseRawData( self.chunkData ) ;
        self.parentContext.runCases() ;
    } ;

    this.readAllLinesFromNodeJsJudgeServer = function( parentContext ) {
        this.parentContext = parentContext ;
        process.stdin.resume() ;
        process.stdin.setEncoding( 'utf8' ) ;
        this.chunkData = '' ;
        process.stdin.on( 'data' , this.readSingleLinesFromNodeJsJudgeServer ) ;
        process.stdin.on( 'end' , this.readEndFromNodeJsJudgeServer ) ;
    } ;

    this.parseRawData = function( data ) {
        var len , i , currentString ;
        len = data.length ;
        currentString = '' ;
        this.allLines = [] ;
        for( i = 0 ; i < len ; i++ ) {
            if( data[ i ] == '\r' ) {
            }
            else if( data[ i ] == '\n' ) {
                this.allLines.push( currentString ) ;
                currentString = '' ;
            }
            else {
                currentString += data[ i ] ;
            }
        }
        if( currentString != '' ) {
            this.allLines.push( currentString ) ;
        }
    } ;

    this.readAllLinesFromFile = function( inputFileName ) {
        var currentDirectory , fsObj , inputFilePath , rawData ;
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            inputFilePath = currentDirectory + '\\' + inputFileName ;
        }
        else {
            //on linux
            inputFilePath = currentDirectory + '/' + inputFileName ;
        }
        rawData = fsObj.readFileSync( inputFilePath , "utf8" ) ;
        this.parseRawData( rawData ) ;
    } ;

    this.next = function( flag ) {
        var len , i , startIdx , res , endIdx ;
        if( flag == 0 ) {
            if( this.currrentCharacterIndex != 0 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            res = '' ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
            }
            this.currrentLineNumber++ ;
            this.currrentCharacterIndex = 0 ;
            return res ;
        }
        while( true ) {
            if( this.currrentLineNumber >= this.allLines.length ) {
                throw new Error( 'No more tokens available!' ) ;
            }
            startIdx = -1 ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) != ' '.charCodeAt( 0 ) ) {
                    startIdx = i ;
                    break ;
                }
            }
            if( startIdx == -1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
                continue ;
            }
            res = '' ;
            endIdx = len - 1 ;
            for( i = startIdx ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) == ' '.charCodeAt( 0 ) ) {
                    endIdx = i ;
                    break ;
                }
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) >= 48 && this.allLines[ this.currrentLineNumber ].charCodeAt( i ) <= 57 ) {
                    res += '' + ( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) - 48 ) ;
                }
                else {
                    res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
                }
            }
            this.currrentCharacterIndex = endIdx ;
            if( endIdx == len - 1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            return res ;
        }
    } ;

    this.nextInt = function() {
        return parseInt( this.next( 1 ) ) ;
    } ;

    this.nextDouble = function() {
        return parseFloat( this.next( 1 ) ) ;
    } ;

    this.nextString = function() {
        return this.next( 1 ) ;
    } ;

    this.nextLine = function() {
        return this.next( 0 ) ;
    } ;
}

function FileOutputHandler() {
    this.resultantStringArray = new Array() ;

    this.addNewLine = function( newString ) {
        this.resultantStringArray.push( newString ) ;
    } ;

    this.clearPercase = function() {
        this.resultantStringArray = new Array() ;
    } ;

    this.flushOutOutputToFile = function( outputFileName ) {
        var i , sz , res , currentDirectory , fsObj , outputFilePath ;
        res = '' ;
        sz = this.resultantStringArray.length ;
        for( i = 0 ; i < sz ; i++ ) {
            if( i != 0 ) {
                res += '\n' ;
            }
            res += this.resultantStringArray[ i ] ;
        }
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            outputFilePath = currentDirectory + '\\' + outputFileName ;
        }
        else {
            //on linux
            outputFilePath = currentDirectory + '/' + outputFileName ;
        }
        fsObj.writeFileSync( outputFilePath , res ) ;
        this.clearPercase() ;
    } ;
}

function CodeExecutioner() {
    this.irObj = new InputReader() ;
    this.psObj = new ProblemSolver() ;
    this.fohObj = new FileOutputHandler() ;

    this.runCases = function() {
		var testCases , hasMoreTestCases , i ;
        if( this.psObj.HAS_TEST_CASES == true ) {
            testCases = this.irObj.nextInt() ;
            for( i = 0 ; i < testCases ; i++ ) {
                this.psObj.clearPerCase() ;
                this.psObj.getInput( this.irObj ) ;
                this.psObj.solveCase() ;
            }
        }
        else {
            while( true ) {
                this.psObj.clearPerCase() ;
                hasMoreTestCases = this.psObj.getInput( this.irObj ) ;
                if( hasMoreTestCases == false ) {
                    break;
                }
                this.psObj.solveCase() ;
            }
        }
        if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
            this.fohObj.flushOutOutputToFile( this.psObj.OUTPUT_FILE_NAME ) ;
        }
    } ;

    this.detectEnvironmentType = function() {
        var environmentType = null ;
        try {
            if( importPackage != null ) {
                environmentType = 'rhino' ;
            }
        }
        catch( ex1 ) {
            try {
                //for nodejs local server check
                if( __dirname != null && ( __dirname.indexOf( 'D:') != -1 || __dirname.indexOf( '/media/') != -1 ) ) {
                    environmentType = 'local-node-js' ;
                }
                else {
                    environmentType = 'server-node-js' ;
                }
            }
            catch( ex2 ) {
                try {
                    if( readline == null || typeof( readline ) != 'function' ) {
                        environmentType = 'server-node-js' ;
                    }
                    else {
                        try {
                            if( Map != null ) {
                                environmentType = 'spider-monkey' ;
                            }
                            else {
                                environmentType = 'javascript-v8' ;
                            }
                        }
                        catch( ex3 ) {
                            environmentType = 'javascript-v8' ;
                        }
                    }
                }
                catch( ex3 ) {
                    environmentType = 'server-node-js' ;
                }
            }
        }
        return environmentType ;
    } ;

    this.configureStreamsAndReadInput = function() {
        var localContext , isNodeJsJudgeServer , environmentType ;
        isNodeJsJudgeServer = false ;
        environmentType = this.detectEnvironmentType() ;
        if( environmentType == 'local-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
                localContext = this.fohObj ;
                print = function() {
                    localContext.addNewLine.apply( localContext , arguments ) ;
                }
            }
            this.irObj.readAllLinesFromFile( this.psObj.INPUT_FILE_NAME ) ;
            this.runCases() ;
        }
        else if( environmentType == 'server-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            this.irObj.readAllLinesFromNodeJsJudgeServer( this ) ;
        }
        else if( environmentType == 'javascript-v8' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
        else if( environmentType == 'rhino' ) {
            this.irObj.readAllLinesFromRhino() ;
            this.runCases() ;
        }
        else if( environmentType == 'spider-monkey' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
    } ;

    this.configureStreamsAndReadInput() ;
}

new CodeExecutioner() ;

function ProblemSolver() {
    this.HAS_TEST_CASES = false ;
    this.INPUT_FILE_NAME = "sample.in" ;
    this.OUTPUT_FILE_NAME = "sample.out" ;
    this.DO_OUTPUT_TO_FILE = false ;
    this.CLEAR_ARRAY_PER_CASE = false ;

    this.solveCase = function() {
        var res , i , j , fl , cn , a , b , c , lo , hi , mi , eps ;
        this.arr = this.arr.sort( function( le , ri ) { return le - ri ; } ) ;
        res = 0 ;
        lo = 0.0 ;
        hi = this.arr[ 0 ] * 1.0 ;
        eps = 1e-10 ;
        cn = 1000 ;
        while( ( hi - lo ) >= eps && cn-- > 0 ) {
            mi = ( lo + hi ) / 2.0 ;
            a = 2.0 * mi ;
            if( mi < this.arr[ 0 ] + eps && a < this.arr[ this.n ] + eps && mi + a < ( this.w / this.n ) + eps ) {
                lo = mi ;
                res = mi * this.n + a * this.n ;
            }
            else {
                hi = mi ;
            }
        }
        print( res.toFixed( 10 ) ) ;
    } ;

    this.init = function() {
        this.lim1 = 100010 ;
        this.lim2 = 110 ;
        this.cc = 1 ;
        this.ind = 1 ;
        this.n = 0 ;
        this.cn = 0 ;
        this.declareAndFillArrays() ;
    } ;

    this.getInput = function( irObj ) {
        var hasMoreInput , i ;
        hasMoreInput = true ;
        try {
        	this.n = irObj.nextInt() ;
        	this.w = irObj.nextInt() ;
            this.arr = [] ;
            for( i = 0 ; i < 2 * this.n ; i++ ) {
                this.arr.push( irObj.nextInt() ) ;
            }
        }
        catch( ex ) {
            hasMoreInput = false ;
        }
        return hasMoreInput ;
    } ;

    this.clearArraysPerCase = function() {
        var i ;
        this.arr = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.arr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
    } ;

    this.clearPerCase = function() {
        this.cn = 0 ;
        this.cc++ ;
        if( this.CLEAR_ARRAY_PER_CASE == true ) {
            this.clearArraysPerCase() ;
        }
    } ;

    this.declareAndFillArrays = function() {
        var i , j ;
        this.srr = new Array() ;
        this.vis = new Array() ;
        this.arr = new Array() ;
        this.brr = new Array() ;
        this.memo = new Array() ;
        this.done = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.srr.push( '' ) ;
            this.vis.push( 0 ) ;
            this.arr.push( 0 ) ;
            this.brr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
        for( i = 0 ; i < this.lim2 ; i++ ) {
            this.memo.push( new Array() ) ;
            this.done.push( new Array() ) ;
            for( j = 0 ; j < this.lim2 ; j++ ) {
                this.memo[ i ].push( -1 ) ;
                this.done[ i ].push( 0 ) ;
            }
        }
    } ;

    this.init() ;
}

function InputReader() {
    var self = this ;
    this.allLines = new Array() ;
    this.currrentLineNumber = 0 ;
    this.currrentCharacterIndex = 0 ;
    this.callBackFunction = null ;
    this.parentContext = null ;

    this.readAllLines = function() {
        var singleLine ;
        while( true ) {
            try {
                singleLine = readline() ;
                if( singleLine == null ) {
                    break ;
                }
            }
            catch( ex ) {
                break ;
            }
            this.allLines.push( singleLine ) ;
        }
    } ;

    this.readAllLinesFromRhino = function() {
        var brObj , line ;
        importPackage( java.io ) ;
        importPackage( java.lang ) ;
        brObj = new BufferedReader( new InputStreamReader( System[ 'in' ] ) ) ;
        this.allLines = [] ;
        while( true ) {
            line = brObj.readLine() ;
            if( line == null ) {
                break;
            }
            this.allLines.push( line ) ;
        }
    } ;

    this.readSingleLinesFromNodeJsJudgeServer = function( chunk ) {
        self.chunkData += chunk ;
    } ;

    this.readEndFromNodeJsJudgeServer = function() {
        self.parseRawData( self.chunkData ) ;
        self.parentContext.runCases() ;
    } ;

    this.readAllLinesFromNodeJsJudgeServer = function( parentContext ) {
        this.parentContext = parentContext ;
        process.stdin.resume() ;
        process.stdin.setEncoding( 'utf8' ) ;
        this.chunkData = '' ;
        process.stdin.on( 'data' , this.readSingleLinesFromNodeJsJudgeServer ) ;
        process.stdin.on( 'end' , this.readEndFromNodeJsJudgeServer ) ;
    } ;

    this.parseRawData = function( data ) {
        var len , i , currentString ;
        len = data.length ;
        currentString = '' ;
        this.allLines = [] ;
        for( i = 0 ; i < len ; i++ ) {
            if( data[ i ] == '\r' ) {
            }
            else if( data[ i ] == '\n' ) {
                this.allLines.push( currentString ) ;
                currentString = '' ;
            }
            else {
                currentString += data[ i ] ;
            }
        }
        if( currentString != '' ) {
            this.allLines.push( currentString ) ;
        }
    } ;

    this.readAllLinesFromFile = function( inputFileName ) {
        var currentDirectory , fsObj , inputFilePath , rawData ;
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            inputFilePath = currentDirectory + '\\' + inputFileName ;
        }
        else {
            //on linux
            inputFilePath = currentDirectory + '/' + inputFileName ;
        }
        rawData = fsObj.readFileSync( inputFilePath , "utf8" ) ;
        this.parseRawData( rawData ) ;
    } ;

    this.next = function( flag ) {
        var len , i , startIdx , res , endIdx ;
        if( flag == 0 ) {
            if( this.currrentCharacterIndex != 0 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            res = '' ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
            }
            this.currrentLineNumber++ ;
            this.currrentCharacterIndex = 0 ;
            return res ;
        }
        while( true ) {
            if( this.currrentLineNumber >= this.allLines.length ) {
                throw new Error( 'No more tokens available!' ) ;
            }
            startIdx = -1 ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) != ' '.charCodeAt( 0 ) ) {
                    startIdx = i ;
                    break ;
                }
            }
            if( startIdx == -1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
                continue ;
            }
            res = '' ;
            endIdx = len - 1 ;
            for( i = startIdx ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) == ' '.charCodeAt( 0 ) ) {
                    endIdx = i ;
                    break ;
                }
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) >= 48 && this.allLines[ this.currrentLineNumber ].charCodeAt( i ) <= 57 ) {
                    res += '' + ( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) - 48 ) ;
                }
                else {
                    res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
                }
            }
            this.currrentCharacterIndex = endIdx ;
            if( endIdx == len - 1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            return res ;
        }
    } ;

    this.nextInt = function() {
        return parseInt( this.next( 1 ) ) ;
    } ;

    this.nextDouble = function() {
        return parseFloat( this.next( 1 ) ) ;
    } ;

    this.nextString = function() {
        return this.next( 1 ) ;
    } ;

    this.nextLine = function() {
        return this.next( 0 ) ;
    } ;
}

function FileOutputHandler() {
    this.resultantStringArray = new Array() ;

    this.addNewLine = function( newString ) {
        this.resultantStringArray.push( newString ) ;
    } ;

    this.clearPercase = function() {
        this.resultantStringArray = new Array() ;
    } ;

    this.flushOutOutputToFile = function( outputFileName ) {
        var i , sz , res , currentDirectory , fsObj , outputFilePath ;
        res = '' ;
        sz = this.resultantStringArray.length ;
        for( i = 0 ; i < sz ; i++ ) {
            if( i != 0 ) {
                res += '\n' ;
            }
            res += this.resultantStringArray[ i ] ;
        }
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            outputFilePath = currentDirectory + '\\' + outputFileName ;
        }
        else {
            //on linux
            outputFilePath = currentDirectory + '/' + outputFileName ;
        }
        fsObj.writeFileSync( outputFilePath , res ) ;
        this.clearPercase() ;
    } ;
}

function CodeExecutioner() {
    this.irObj = new InputReader() ;
    this.psObj = new ProblemSolver() ;
    this.fohObj = new FileOutputHandler() ;

    this.runCases = function() {
		var testCases , hasMoreTestCases , i ;
        if( this.psObj.HAS_TEST_CASES == true ) {
            testCases = this.irObj.nextInt() ;
            for( i = 0 ; i < testCases ; i++ ) {
                this.psObj.clearPerCase() ;
                this.psObj.getInput( this.irObj ) ;
                this.psObj.solveCase() ;
            }
        }
        else {
            while( true ) {
                this.psObj.clearPerCase() ;
                hasMoreTestCases = this.psObj.getInput( this.irObj ) ;
                if( hasMoreTestCases == false ) {
                    break;
                }
                this.psObj.solveCase() ;
            }
        }
        if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
            this.fohObj.flushOutOutputToFile( this.psObj.OUTPUT_FILE_NAME ) ;
        }
    } ;

    this.detectEnvironmentType = function() {
        var environmentType = null ;
        try {
            if( importPackage != null ) {
                environmentType = 'rhino' ;
            }
        }
        catch( ex1 ) {
            try {
                //for nodejs local server check
                if( __dirname != null && ( __dirname.indexOf( 'D:') != -1 || __dirname.indexOf( '/media/') != -1 ) ) {
                    environmentType = 'local-node-js' ;
                }
                else {
                    environmentType = 'server-node-js' ;
                }
            }
            catch( ex2 ) {
                try {
                    if( readline == null || typeof( readline ) != 'function' ) {
                        environmentType = 'server-node-js' ;
                    }
                    else {
                        try {
                            if( Map != null ) {
                                environmentType = 'spider-monkey' ;
                            }
                            else {
                                environmentType = 'javascript-v8' ;
                            }
                        }
                        catch( ex3 ) {
                            environmentType = 'javascript-v8' ;
                        }
                    }
                }
                catch( ex3 ) {
                    environmentType = 'server-node-js' ;
                }
            }
        }
        return environmentType ;
    } ;

    this.configureStreamsAndReadInput = function() {
        var localContext , isNodeJsJudgeServer , environmentType ;
        isNodeJsJudgeServer = false ;
        environmentType = this.detectEnvironmentType() ;
        if( environmentType == 'local-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
                localContext = this.fohObj ;
                print = function() {
                    localContext.addNewLine.apply( localContext , arguments ) ;
                }
            }
            this.irObj.readAllLinesFromFile( this.psObj.INPUT_FILE_NAME ) ;
            this.runCases() ;
        }
        else if( environmentType == 'server-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            this.irObj.readAllLinesFromNodeJsJudgeServer( this ) ;
        }
        else if( environmentType == 'javascript-v8' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
        else if( environmentType == 'rhino' ) {
            this.irObj.readAllLinesFromRhino() ;
            this.runCases() ;
        }
        else if( environmentType == 'spider-monkey' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
    } ;

    this.configureStreamsAndReadInput() ;
}

new CodeExecutioner() ;

function ProblemSolver() {
    this.HAS_TEST_CASES = false ;
    this.INPUT_FILE_NAME = "sample.in" ;
    this.OUTPUT_FILE_NAME = "sample.out" ;
    this.DO_OUTPUT_TO_FILE = false ;
    this.CLEAR_ARRAY_PER_CASE = false ;

    this.solveCase = function() {
        var res , i , j , fl , cn , a , b , c , lo , hi , mi , eps ;
        this.arr = this.arr.sort( function( le , ri ) { return le - ri ; } ) ;
        res = 0 ;
        lo = 0.0 ;
        hi = this.arr[ 0 ] * 1.0 ;
        eps = 1e-9 ;
        cn = 100 ;
        while( ( hi - lo ) >= eps && cn-- > 0 ) {
            mi = ( lo + hi ) / 2.0 ;
            a = 2.0 * mi ;
            if( mi < this.arr[ 0 ] + eps && a < this.arr[ this.n ] + eps && mi * this.n + a * this.n < this.w + eps ) {
                lo = mi ;
                res = mi * this.n + a * this.n ;
            }
            else {
                hi = mi ;
            }
        }
        print( res.toFixed( 10 ) ) ;
    } ;

    this.init = function() {
        this.lim1 = 100010 ;
        this.lim2 = 110 ;
        this.cc = 1 ;
        this.ind = 1 ;
        this.n = 0 ;
        this.cn = 0 ;
        this.declareAndFillArrays() ;
    } ;

    this.getInput = function( irObj ) {
        var hasMoreInput , i ;
        hasMoreInput = true ;
        try {
        	this.n = irObj.nextInt() ;
        	this.w = irObj.nextInt() ;
            this.arr = [] ;
            for( i = 0 ; i < 2 * this.n ; i++ ) {
                this.arr.push( irObj.nextInt() ) ;
            }
        }
        catch( ex ) {
            hasMoreInput = false ;
        }
        return hasMoreInput ;
    } ;

    this.clearArraysPerCase = function() {
        var i ;
        this.arr = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.arr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
    } ;

    this.clearPerCase = function() {
        this.cn = 0 ;
        this.cc++ ;
        if( this.CLEAR_ARRAY_PER_CASE == true ) {
            this.clearArraysPerCase() ;
        }
    } ;

    this.declareAndFillArrays = function() {
        var i , j ;
        this.srr = new Array() ;
        this.vis = new Array() ;
        this.arr = new Array() ;
        this.brr = new Array() ;
        this.memo = new Array() ;
        this.done = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.srr.push( '' ) ;
            this.vis.push( 0 ) ;
            this.arr.push( 0 ) ;
            this.brr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
        for( i = 0 ; i < this.lim2 ; i++ ) {
            this.memo.push( new Array() ) ;
            this.done.push( new Array() ) ;
            for( j = 0 ; j < this.lim2 ; j++ ) {
                this.memo[ i ].push( -1 ) ;
                this.done[ i ].push( 0 ) ;
            }
        }
    } ;

    this.init() ;
}

function InputReader() {
    var self = this ;
    this.allLines = new Array() ;
    this.currrentLineNumber = 0 ;
    this.currrentCharacterIndex = 0 ;
    this.callBackFunction = null ;
    this.parentContext = null ;

    this.readAllLines = function() {
        var singleLine ;
        while( true ) {
            try {
                singleLine = readline() ;
                if( singleLine == null ) {
                    break ;
                }
            }
            catch( ex ) {
                break ;
            }
            this.allLines.push( singleLine ) ;
        }
    } ;

    this.readAllLinesFromRhino = function() {
        var brObj , line ;
        importPackage( java.io ) ;
        importPackage( java.lang ) ;
        brObj = new BufferedReader( new InputStreamReader( System[ 'in' ] ) ) ;
        this.allLines = [] ;
        while( true ) {
            line = brObj.readLine() ;
            if( line == null ) {
                break;
            }
            this.allLines.push( line ) ;
        }
    } ;

    this.readSingleLinesFromNodeJsJudgeServer = function( chunk ) {
        self.chunkData += chunk ;
    } ;

    this.readEndFromNodeJsJudgeServer = function() {
        self.parseRawData( self.chunkData ) ;
        self.parentContext.runCases() ;
    } ;

    this.readAllLinesFromNodeJsJudgeServer = function( parentContext ) {
        this.parentContext = parentContext ;
        process.stdin.resume() ;
        process.stdin.setEncoding( 'utf8' ) ;
        this.chunkData = '' ;
        process.stdin.on( 'data' , this.readSingleLinesFromNodeJsJudgeServer ) ;
        process.stdin.on( 'end' , this.readEndFromNodeJsJudgeServer ) ;
    } ;

    this.parseRawData = function( data ) {
        var len , i , currentString ;
        len = data.length ;
        currentString = '' ;
        this.allLines = [] ;
        for( i = 0 ; i < len ; i++ ) {
            if( data[ i ] == '\r' ) {
            }
            else if( data[ i ] == '\n' ) {
                this.allLines.push( currentString ) ;
                currentString = '' ;
            }
            else {
                currentString += data[ i ] ;
            }
        }
        if( currentString != '' ) {
            this.allLines.push( currentString ) ;
        }
    } ;

    this.readAllLinesFromFile = function( inputFileName ) {
        var currentDirectory , fsObj , inputFilePath , rawData ;
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            inputFilePath = currentDirectory + '\\' + inputFileName ;
        }
        else {
            //on linux
            inputFilePath = currentDirectory + '/' + inputFileName ;
        }
        rawData = fsObj.readFileSync( inputFilePath , "utf8" ) ;
        this.parseRawData( rawData ) ;
    } ;

    this.next = function( flag ) {
        var len , i , startIdx , res , endIdx ;
        if( flag == 0 ) {
            if( this.currrentCharacterIndex != 0 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            res = '' ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
            }
            this.currrentLineNumber++ ;
            this.currrentCharacterIndex = 0 ;
            return res ;
        }
        while( true ) {
            if( this.currrentLineNumber >= this.allLines.length ) {
                throw new Error( 'No more tokens available!' ) ;
            }
            startIdx = -1 ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) != ' '.charCodeAt( 0 ) ) {
                    startIdx = i ;
                    break ;
                }
            }
            if( startIdx == -1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
                continue ;
            }
            res = '' ;
            endIdx = len - 1 ;
            for( i = startIdx ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) == ' '.charCodeAt( 0 ) ) {
                    endIdx = i ;
                    break ;
                }
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) >= 48 && this.allLines[ this.currrentLineNumber ].charCodeAt( i ) <= 57 ) {
                    res += '' + ( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) - 48 ) ;
                }
                else {
                    res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
                }
            }
            this.currrentCharacterIndex = endIdx ;
            if( endIdx == len - 1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            return res ;
        }
    } ;

    this.nextInt = function() {
        return parseInt( this.next( 1 ) ) ;
    } ;

    this.nextDouble = function() {
        return parseFloat( this.next( 1 ) ) ;
    } ;

    this.nextString = function() {
        return this.next( 1 ) ;
    } ;

    this.nextLine = function() {
        return this.next( 0 ) ;
    } ;
}

function FileOutputHandler() {
    this.resultantStringArray = new Array() ;

    this.addNewLine = function( newString ) {
        this.resultantStringArray.push( newString ) ;
    } ;

    this.clearPercase = function() {
        this.resultantStringArray = new Array() ;
    } ;

    this.flushOutOutputToFile = function( outputFileName ) {
        var i , sz , res , currentDirectory , fsObj , outputFilePath ;
        res = '' ;
        sz = this.resultantStringArray.length ;
        for( i = 0 ; i < sz ; i++ ) {
            if( i != 0 ) {
                res += '\n' ;
            }
            res += this.resultantStringArray[ i ] ;
        }
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            outputFilePath = currentDirectory + '\\' + outputFileName ;
        }
        else {
            //on linux
            outputFilePath = currentDirectory + '/' + outputFileName ;
        }
        fsObj.writeFileSync( outputFilePath , res ) ;
        this.clearPercase() ;
    } ;
}

function CodeExecutioner() {
    this.irObj = new InputReader() ;
    this.psObj = new ProblemSolver() ;
    this.fohObj = new FileOutputHandler() ;

    this.runCases = function() {
		var testCases , hasMoreTestCases , i ;
        if( this.psObj.HAS_TEST_CASES == true ) {
            testCases = this.irObj.nextInt() ;
            for( i = 0 ; i < testCases ; i++ ) {
                this.psObj.clearPerCase() ;
                this.psObj.getInput( this.irObj ) ;
                this.psObj.solveCase() ;
            }
        }
        else {
            while( true ) {
                this.psObj.clearPerCase() ;
                hasMoreTestCases = this.psObj.getInput( this.irObj ) ;
                if( hasMoreTestCases == false ) {
                    break;
                }
                this.psObj.solveCase() ;
            }
        }
        if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
            this.fohObj.flushOutOutputToFile( this.psObj.OUTPUT_FILE_NAME ) ;
        }
    } ;

    this.detectEnvironmentType = function() {
        var environmentType = null ;
        try {
            if( importPackage != null ) {
                environmentType = 'rhino' ;
            }
        }
        catch( ex1 ) {
            try {
                //for nodejs local server check
                if( __dirname != null && ( __dirname.indexOf( 'D:') != -1 || __dirname.indexOf( '/media/') != -1 ) ) {
                    environmentType = 'local-node-js' ;
                }
                else {
                    environmentType = 'server-node-js' ;
                }
            }
            catch( ex2 ) {
                try {
                    if( readline == null || typeof( readline ) != 'function' ) {
                        environmentType = 'server-node-js' ;
                    }
                    else {
                        try {
                            if( Map != null ) {
                                environmentType = 'spider-monkey' ;
                            }
                            else {
                                environmentType = 'javascript-v8' ;
                            }
                        }
                        catch( ex3 ) {
                            environmentType = 'javascript-v8' ;
                        }
                    }
                }
                catch( ex3 ) {
                    environmentType = 'server-node-js' ;
                }
            }
        }
        return environmentType ;
    } ;

    this.configureStreamsAndReadInput = function() {
        var localContext , isNodeJsJudgeServer , environmentType ;
        isNodeJsJudgeServer = false ;
        environmentType = this.detectEnvironmentType() ;
        if( environmentType == 'local-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
                localContext = this.fohObj ;
                print = function() {
                    localContext.addNewLine.apply( localContext , arguments ) ;
                }
            }
            this.irObj.readAllLinesFromFile( this.psObj.INPUT_FILE_NAME ) ;
            this.runCases() ;
        }
        else if( environmentType == 'server-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            this.irObj.readAllLinesFromNodeJsJudgeServer( this ) ;
        }
        else if( environmentType == 'javascript-v8' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
        else if( environmentType == 'rhino' ) {
            this.irObj.readAllLinesFromRhino() ;
            this.runCases() ;
        }
        else if( environmentType == 'spider-monkey' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
    } ;

    this.configureStreamsAndReadInput() ;
}

new CodeExecutioner() ;

function ProblemSolver() {
    this.HAS_TEST_CASES = false ;
    this.INPUT_FILE_NAME = "sample.in" ;
    this.OUTPUT_FILE_NAME = "sample.out" ;
    this.DO_OUTPUT_TO_FILE = false ;
    this.CLEAR_ARRAY_PER_CASE = false ;

    this.solveCase = function() {
        var res , i , j , fl , cn , a , b , c , lo , hi , mi , eps ;
        this.arr = this.arr.sort( function( le , ri ) { return le - ri ; } ) ;
        res = 0 ;
        lo = 0.0 ;
        hi = this.arr[ 0 ] * 1.0 ;
        eps = 1e-9 ;
        cn = 1000000 ;
        while( ( hi - lo ) >= eps && cn-- > 0 ) {
            mi = ( lo + hi ) / 2.0 ;
            a = 2.0 * mi ;
            if( mi < this.arr[ 0 ] + eps && a < this.arr[ this.n ] + eps && mi + a < ( this.w / this.n ) + eps ) {
                lo = mi ;
                res = mi * this.n + a * this.n ;
            }
            else {
                hi = mi ;
            }
        }
        print( res.toFixed( 10 ) ) ;
    } ;

    this.init = function() {
        this.lim1 = 100010 ;
        this.lim2 = 110 ;
        this.cc = 1 ;
        this.ind = 1 ;
        this.n = 0 ;
        this.cn = 0 ;
        this.declareAndFillArrays() ;
    } ;

    this.getInput = function( irObj ) {
        var hasMoreInput , i ;
        hasMoreInput = true ;
        try {
        	this.n = irObj.nextInt() ;
        	this.w = irObj.nextInt() ;
            this.arr = [] ;
            for( i = 0 ; i < 2 * this.n ; i++ ) {
                this.arr.push( irObj.nextInt() ) ;
            }
        }
        catch( ex ) {
            hasMoreInput = false ;
        }
        return hasMoreInput ;
    } ;

    this.clearArraysPerCase = function() {
        var i ;
        this.arr = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.arr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
    } ;

    this.clearPerCase = function() {
        this.cn = 0 ;
        this.cc++ ;
        if( this.CLEAR_ARRAY_PER_CASE == true ) {
            this.clearArraysPerCase() ;
        }
    } ;

    this.declareAndFillArrays = function() {
        var i , j ;
        this.srr = new Array() ;
        this.vis = new Array() ;
        this.arr = new Array() ;
        this.brr = new Array() ;
        this.memo = new Array() ;
        this.done = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.srr.push( '' ) ;
            this.vis.push( 0 ) ;
            this.arr.push( 0 ) ;
            this.brr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
        for( i = 0 ; i < this.lim2 ; i++ ) {
            this.memo.push( new Array() ) ;
            this.done.push( new Array() ) ;
            for( j = 0 ; j < this.lim2 ; j++ ) {
                this.memo[ i ].push( -1 ) ;
                this.done[ i ].push( 0 ) ;
            }
        }
    } ;

    this.init() ;
}

function InputReader() {
    var self = this ;
    this.allLines = new Array() ;
    this.currrentLineNumber = 0 ;
    this.currrentCharacterIndex = 0 ;
    this.callBackFunction = null ;
    this.parentContext = null ;

    this.readAllLines = function() {
        var singleLine ;
        while( true ) {
            try {
                singleLine = readline() ;
                if( singleLine == null ) {
                    break ;
                }
            }
            catch( ex ) {
                break ;
            }
            this.allLines.push( singleLine ) ;
        }
    } ;

    this.readAllLinesFromRhino = function() {
        var brObj , line ;
        importPackage( java.io ) ;
        importPackage( java.lang ) ;
        brObj = new BufferedReader( new InputStreamReader( System[ 'in' ] ) ) ;
        this.allLines = [] ;
        while( true ) {
            line = brObj.readLine() ;
            if( line == null ) {
                break;
            }
            this.allLines.push( line ) ;
        }
    } ;

    this.readSingleLinesFromNodeJsJudgeServer = function( chunk ) {
        self.chunkData += chunk ;
    } ;

    this.readEndFromNodeJsJudgeServer = function() {
        self.parseRawData( self.chunkData ) ;
        self.parentContext.runCases() ;
    } ;

    this.readAllLinesFromNodeJsJudgeServer = function( parentContext ) {
        this.parentContext = parentContext ;
        process.stdin.resume() ;
        process.stdin.setEncoding( 'utf8' ) ;
        this.chunkData = '' ;
        process.stdin.on( 'data' , this.readSingleLinesFromNodeJsJudgeServer ) ;
        process.stdin.on( 'end' , this.readEndFromNodeJsJudgeServer ) ;
    } ;

    this.parseRawData = function( data ) {
        var len , i , currentString ;
        len = data.length ;
        currentString = '' ;
        this.allLines = [] ;
        for( i = 0 ; i < len ; i++ ) {
            if( data[ i ] == '\r' ) {
            }
            else if( data[ i ] == '\n' ) {
                this.allLines.push( currentString ) ;
                currentString = '' ;
            }
            else {
                currentString += data[ i ] ;
            }
        }
        if( currentString != '' ) {
            this.allLines.push( currentString ) ;
        }
    } ;

    this.readAllLinesFromFile = function( inputFileName ) {
        var currentDirectory , fsObj , inputFilePath , rawData ;
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            inputFilePath = currentDirectory + '\\' + inputFileName ;
        }
        else {
            //on linux
            inputFilePath = currentDirectory + '/' + inputFileName ;
        }
        rawData = fsObj.readFileSync( inputFilePath , "utf8" ) ;
        this.parseRawData( rawData ) ;
    } ;

    this.next = function( flag ) {
        var len , i , startIdx , res , endIdx ;
        if( flag == 0 ) {
            if( this.currrentCharacterIndex != 0 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            res = '' ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
            }
            this.currrentLineNumber++ ;
            this.currrentCharacterIndex = 0 ;
            return res ;
        }
        while( true ) {
            if( this.currrentLineNumber >= this.allLines.length ) {
                throw new Error( 'No more tokens available!' ) ;
            }
            startIdx = -1 ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) != ' '.charCodeAt( 0 ) ) {
                    startIdx = i ;
                    break ;
                }
            }
            if( startIdx == -1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
                continue ;
            }
            res = '' ;
            endIdx = len - 1 ;
            for( i = startIdx ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) == ' '.charCodeAt( 0 ) ) {
                    endIdx = i ;
                    break ;
                }
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) >= 48 && this.allLines[ this.currrentLineNumber ].charCodeAt( i ) <= 57 ) {
                    res += '' + ( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) - 48 ) ;
                }
                else {
                    res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
                }
            }
            this.currrentCharacterIndex = endIdx ;
            if( endIdx == len - 1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            return res ;
        }
    } ;

    this.nextInt = function() {
        return parseInt( this.next( 1 ) ) ;
    } ;

    this.nextDouble = function() {
        return parseFloat( this.next( 1 ) ) ;
    } ;

    this.nextString = function() {
        return this.next( 1 ) ;
    } ;

    this.nextLine = function() {
        return this.next( 0 ) ;
    } ;
}

function FileOutputHandler() {
    this.resultantStringArray = new Array() ;

    this.addNewLine = function( newString ) {
        this.resultantStringArray.push( newString ) ;
    } ;

    this.clearPercase = function() {
        this.resultantStringArray = new Array() ;
    } ;

    this.flushOutOutputToFile = function( outputFileName ) {
        var i , sz , res , currentDirectory , fsObj , outputFilePath ;
        res = '' ;
        sz = this.resultantStringArray.length ;
        for( i = 0 ; i < sz ; i++ ) {
            if( i != 0 ) {
                res += '\n' ;
            }
            res += this.resultantStringArray[ i ] ;
        }
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            outputFilePath = currentDirectory + '\\' + outputFileName ;
        }
        else {
            //on linux
            outputFilePath = currentDirectory + '/' + outputFileName ;
        }
        fsObj.writeFileSync( outputFilePath , res ) ;
        this.clearPercase() ;
    } ;
}

function CodeExecutioner() {
    this.irObj = new InputReader() ;
    this.psObj = new ProblemSolver() ;
    this.fohObj = new FileOutputHandler() ;

    this.runCases = function() {
		var testCases , hasMoreTestCases , i ;
        if( this.psObj.HAS_TEST_CASES == true ) {
            testCases = this.irObj.nextInt() ;
            for( i = 0 ; i < testCases ; i++ ) {
                this.psObj.clearPerCase() ;
                this.psObj.getInput( this.irObj ) ;
                this.psObj.solveCase() ;
            }
        }
        else {
            while( true ) {
                this.psObj.clearPerCase() ;
                hasMoreTestCases = this.psObj.getInput( this.irObj ) ;
                if( hasMoreTestCases == false ) {
                    break;
                }
                this.psObj.solveCase() ;
            }
        }
        if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
            this.fohObj.flushOutOutputToFile( this.psObj.OUTPUT_FILE_NAME ) ;
        }
    } ;

    this.detectEnvironmentType = function() {
        var environmentType = null ;
        try {
            if( importPackage != null ) {
                environmentType = 'rhino' ;
            }
        }
        catch( ex1 ) {
            try {
                //for nodejs local server check
                if( __dirname != null && ( __dirname.indexOf( 'D:') != -1 || __dirname.indexOf( '/media/') != -1 ) ) {
                    environmentType = 'local-node-js' ;
                }
                else {
                    environmentType = 'server-node-js' ;
                }
            }
            catch( ex2 ) {
                try {
                    if( readline == null || typeof( readline ) != 'function' ) {
                        environmentType = 'server-node-js' ;
                    }
                    else {
                        try {
                            if( Map != null ) {
                                environmentType = 'spider-monkey' ;
                            }
                            else {
                                environmentType = 'javascript-v8' ;
                            }
                        }
                        catch( ex3 ) {
                            environmentType = 'javascript-v8' ;
                        }
                    }
                }
                catch( ex3 ) {
                    environmentType = 'server-node-js' ;
                }
            }
        }
        return environmentType ;
    } ;

    this.configureStreamsAndReadInput = function() {
        var localContext , isNodeJsJudgeServer , environmentType ;
        isNodeJsJudgeServer = false ;
        environmentType = this.detectEnvironmentType() ;
        if( environmentType == 'local-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
                localContext = this.fohObj ;
                print = function() {
                    localContext.addNewLine.apply( localContext , arguments ) ;
                }
            }
            this.irObj.readAllLinesFromFile( this.psObj.INPUT_FILE_NAME ) ;
            this.runCases() ;
        }
        else if( environmentType == 'server-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            this.irObj.readAllLinesFromNodeJsJudgeServer( this ) ;
        }
        else if( environmentType == 'javascript-v8' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
        else if( environmentType == 'rhino' ) {
            this.irObj.readAllLinesFromRhino() ;
            this.runCases() ;
        }
        else if( environmentType == 'spider-monkey' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
    } ;

    this.configureStreamsAndReadInput() ;
}

new CodeExecutioner() ;

function ProblemSolver() {
    this.HAS_TEST_CASES = false ;
    this.INPUT_FILE_NAME = "sample.in" ;
    this.OUTPUT_FILE_NAME = "sample.out" ;
    this.DO_OUTPUT_TO_FILE = false ;
    this.CLEAR_ARRAY_PER_CASE = false ;

    this.solveCase = function() {
        var res , i , j , fl , cn , a , b , c , lo , hi , mi , eps ;
        this.arr = this.arr.sort( function( le , ri ) { return le - ri ; } ) ;
        res = 0 ;
        lo = 0.0 ;
        hi = this.arr[ 0 ] * 1.0 ;
        eps = 1e-9 ;
        cn = 1000000 ;
        while( ( hi - lo ) >= eps && cn-- > 0 ) {
            mi = ( lo + hi ) / 2.0 ;
            a = 2.0 * mi ;
            if( mi < this.arr[ 0 ] + eps && a < this.arr[ this.n ] + eps && mi * this.n < this.w + eps && a * this.n < this.w + eps && mi * this.n + a * this.n < this.w + eps ) {
                lo = mi ;
                res = mi * this.n + a * this.n ;
            }
            else {
                hi = mi ;
            }
        }
        print( res.toFixed( 10 ) ) ;
    } ;

    this.init = function() {
        this.lim1 = 100010 ;
        this.lim2 = 110 ;
        this.cc = 1 ;
        this.ind = 1 ;
        this.n = 0 ;
        this.cn = 0 ;
        this.declareAndFillArrays() ;
    } ;

    this.getInput = function( irObj ) {
        var hasMoreInput , i ;
        hasMoreInput = true ;
        try {
        	this.n = irObj.nextInt() ;
        	this.w = irObj.nextInt() ;
            this.arr = [] ;
            for( i = 0 ; i < 2 * this.n ; i++ ) {
                this.arr.push( irObj.nextInt() ) ;
            }
        }
        catch( ex ) {
            hasMoreInput = false ;
        }
        return hasMoreInput ;
    } ;

    this.clearArraysPerCase = function() {
        var i ;
        this.arr = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.arr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
    } ;

    this.clearPerCase = function() {
        this.cn = 0 ;
        this.cc++ ;
        if( this.CLEAR_ARRAY_PER_CASE == true ) {
            this.clearArraysPerCase() ;
        }
    } ;

    this.declareAndFillArrays = function() {
        var i , j ;
        this.srr = new Array() ;
        this.vis = new Array() ;
        this.arr = new Array() ;
        this.brr = new Array() ;
        this.memo = new Array() ;
        this.done = new Array() ;
        this.adjList = new Array() ;
        for( i = 0 ; i < this.lim1 ; i++ ) {
            this.srr.push( '' ) ;
            this.vis.push( 0 ) ;
            this.arr.push( 0 ) ;
            this.brr.push( 0 ) ;
            this.adjList.push( new Array() ) ;
        }
        for( i = 0 ; i < this.lim2 ; i++ ) {
            this.memo.push( new Array() ) ;
            this.done.push( new Array() ) ;
            for( j = 0 ; j < this.lim2 ; j++ ) {
                this.memo[ i ].push( -1 ) ;
                this.done[ i ].push( 0 ) ;
            }
        }
    } ;

    this.init() ;
}

function InputReader() {
    var self = this ;
    this.allLines = new Array() ;
    this.currrentLineNumber = 0 ;
    this.currrentCharacterIndex = 0 ;
    this.callBackFunction = null ;
    this.parentContext = null ;

    this.readAllLines = function() {
        var singleLine ;
        while( true ) {
            try {
                singleLine = readline() ;
                if( singleLine == null ) {
                    break ;
                }
            }
            catch( ex ) {
                break ;
            }
            this.allLines.push( singleLine ) ;
        }
    } ;

    this.readAllLinesFromRhino = function() {
        var brObj , line ;
        importPackage( java.io ) ;
        importPackage( java.lang ) ;
        brObj = new BufferedReader( new InputStreamReader( System[ 'in' ] ) ) ;
        this.allLines = [] ;
        while( true ) {
            line = brObj.readLine() ;
            if( line == null ) {
                break;
            }
            this.allLines.push( line ) ;
        }
    } ;

    this.readSingleLinesFromNodeJsJudgeServer = function( chunk ) {
        self.chunkData += chunk ;
    } ;

    this.readEndFromNodeJsJudgeServer = function() {
        self.parseRawData( self.chunkData ) ;
        self.parentContext.runCases() ;
    } ;

    this.readAllLinesFromNodeJsJudgeServer = function( parentContext ) {
        this.parentContext = parentContext ;
        process.stdin.resume() ;
        process.stdin.setEncoding( 'utf8' ) ;
        this.chunkData = '' ;
        process.stdin.on( 'data' , this.readSingleLinesFromNodeJsJudgeServer ) ;
        process.stdin.on( 'end' , this.readEndFromNodeJsJudgeServer ) ;
    } ;

    this.parseRawData = function( data ) {
        var len , i , currentString ;
        len = data.length ;
        currentString = '' ;
        this.allLines = [] ;
        for( i = 0 ; i < len ; i++ ) {
            if( data[ i ] == '\r' ) {
            }
            else if( data[ i ] == '\n' ) {
                this.allLines.push( currentString ) ;
                currentString = '' ;
            }
            else {
                currentString += data[ i ] ;
            }
        }
        if( currentString != '' ) {
            this.allLines.push( currentString ) ;
        }
    } ;

    this.readAllLinesFromFile = function( inputFileName ) {
        var currentDirectory , fsObj , inputFilePath , rawData ;
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            inputFilePath = currentDirectory + '\\' + inputFileName ;
        }
        else {
            //on linux
            inputFilePath = currentDirectory + '/' + inputFileName ;
        }
        rawData = fsObj.readFileSync( inputFilePath , "utf8" ) ;
        this.parseRawData( rawData ) ;
    } ;

    this.next = function( flag ) {
        var len , i , startIdx , res , endIdx ;
        if( flag == 0 ) {
            if( this.currrentCharacterIndex != 0 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            res = '' ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
            }
            this.currrentLineNumber++ ;
            this.currrentCharacterIndex = 0 ;
            return res ;
        }
        while( true ) {
            if( this.currrentLineNumber >= this.allLines.length ) {
                throw new Error( 'No more tokens available!' ) ;
            }
            startIdx = -1 ;
            len = this.allLines[ this.currrentLineNumber ].length ;
            if( typeof( len ) == 'function' ) {
                len = this.allLines[ this.currrentLineNumber ].length() ;
            }
            for( i = this.currrentCharacterIndex ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) != ' '.charCodeAt( 0 ) ) {
                    startIdx = i ;
                    break ;
                }
            }
            if( startIdx == -1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
                continue ;
            }
            res = '' ;
            endIdx = len - 1 ;
            for( i = startIdx ; i < len ; i++ ) {
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) == ' '.charCodeAt( 0 ) ) {
                    endIdx = i ;
                    break ;
                }
                if( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) >= 48 && this.allLines[ this.currrentLineNumber ].charCodeAt( i ) <= 57 ) {
                    res += '' + ( this.allLines[ this.currrentLineNumber ].charCodeAt( i ) - 48 ) ;
                }
                else {
                    res += '' + this.allLines[ this.currrentLineNumber ].charAt( i ) ;
                }
            }
            this.currrentCharacterIndex = endIdx ;
            if( endIdx == len - 1 ) {
                this.currrentLineNumber++ ;
                this.currrentCharacterIndex = 0 ;
            }
            return res ;
        }
    } ;

    this.nextInt = function() {
        return parseInt( this.next( 1 ) ) ;
    } ;

    this.nextDouble = function() {
        return parseFloat( this.next( 1 ) ) ;
    } ;

    this.nextString = function() {
        return this.next( 1 ) ;
    } ;

    this.nextLine = function() {
        return this.next( 0 ) ;
    } ;
}

function FileOutputHandler() {
    this.resultantStringArray = new Array() ;

    this.addNewLine = function( newString ) {
        this.resultantStringArray.push( newString ) ;
    } ;

    this.clearPercase = function() {
        this.resultantStringArray = new Array() ;
    } ;

    this.flushOutOutputToFile = function( outputFileName ) {
        var i , sz , res , currentDirectory , fsObj , outputFilePath ;
        res = '' ;
        sz = this.resultantStringArray.length ;
        for( i = 0 ; i < sz ; i++ ) {
            if( i != 0 ) {
                res += '\n' ;
            }
            res += this.resultantStringArray[ i ] ;
        }
        fsObj = require( 'fs' ) ;
        currentDirectory = __dirname ;
        if( currentDirectory.indexOf( 'D:' ) != -1 ) {
            //on windows
            outputFilePath = currentDirectory + '\\' + outputFileName ;
        }
        else {
            //on linux
            outputFilePath = currentDirectory + '/' + outputFileName ;
        }
        fsObj.writeFileSync( outputFilePath , res ) ;
        this.clearPercase() ;
    } ;
}

function CodeExecutioner() {
    this.irObj = new InputReader() ;
    this.psObj = new ProblemSolver() ;
    this.fohObj = new FileOutputHandler() ;

    this.runCases = function() {
		var testCases , hasMoreTestCases , i ;
        if( this.psObj.HAS_TEST_CASES == true ) {
            testCases = this.irObj.nextInt() ;
            for( i = 0 ; i < testCases ; i++ ) {
                this.psObj.clearPerCase() ;
                this.psObj.getInput( this.irObj ) ;
                this.psObj.solveCase() ;
            }
        }
        else {
            while( true ) {
                this.psObj.clearPerCase() ;
                hasMoreTestCases = this.psObj.getInput( this.irObj ) ;
                if( hasMoreTestCases == false ) {
                    break;
                }
                this.psObj.solveCase() ;
            }
        }
        if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
            this.fohObj.flushOutOutputToFile( this.psObj.OUTPUT_FILE_NAME ) ;
        }
    } ;

    this.detectEnvironmentType = function() {
        var environmentType = null ;
        try {
            if( importPackage != null ) {
                environmentType = 'rhino' ;
            }
        }
        catch( ex1 ) {
            try {
                //for nodejs local server check
                if( __dirname != null && ( __dirname.indexOf( 'D:') != -1 || __dirname.indexOf( '/media/') != -1 ) ) {
                    environmentType = 'local-node-js' ;
                }
                else {
                    environmentType = 'server-node-js' ;
                }
            }
            catch( ex2 ) {
                try {
                    if( readline == null || typeof( readline ) != 'function' ) {
                        environmentType = 'server-node-js' ;
                    }
                    else {
                        try {
                            if( Map != null ) {
                                environmentType = 'spider-monkey' ;
                            }
                            else {
                                environmentType = 'javascript-v8' ;
                            }
                        }
                        catch( ex3 ) {
                            environmentType = 'javascript-v8' ;
                        }
                    }
                }
                catch( ex3 ) {
                    environmentType = 'server-node-js' ;
                }
            }
        }
        return environmentType ;
    } ;

    this.configureStreamsAndReadInput = function() {
        var localContext , isNodeJsJudgeServer , environmentType ;
        isNodeJsJudgeServer = false ;
        environmentType = this.detectEnvironmentType() ;
        if( environmentType == 'local-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            if( this.psObj.DO_OUTPUT_TO_FILE == true ) {
                localContext = this.fohObj ;
                print = function() {
                    localContext.addNewLine.apply( localContext , arguments ) ;
                }
            }
            this.irObj.readAllLinesFromFile( this.psObj.INPUT_FILE_NAME ) ;
            this.runCases() ;
        }
        else if( environmentType == 'server-node-js' ) {
            try {
                if( print == null || typeof( print ) != 'function' ) {
                    print = console.log ;
                }
            }
            catch( ex ) {
                print = console.log ;
            }
            this.irObj.readAllLinesFromNodeJsJudgeServer( this ) ;
        }
        else if( environmentType == 'javascript-v8' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
        else if( environmentType == 'rhino' ) {
            this.irObj.readAllLinesFromRhino() ;
            this.runCases() ;
        }
        else if( environmentType == 'spider-monkey' ) {
            this.irObj.readAllLines() ;
            this.runCases() ;
        }
    } ;

    this.configureStreamsAndReadInput() ;
}

new CodeExecutioner() ;

'use strict';

process.stdin.resume();
process.stdin.setEncoding('utf-8');

let inputString = '';
let currentLine = 0;

process.stdin.on('data', inputStdin => {
    inputString += inputStdin;
});

process.stdin.on('end', _ => {
    inputString = inputString.trim().split('\n').map(string => {
        return string.trim();
    });

    main();
});

function readLine() {
    return inputString[currentLine++];
}

function printResult(x) {
    process.stdout.write(x);
}

function main() {
    const nw = readLine().split(' ').map(Number);
    const arr = readLine().split(' ').map(Number);

    const result = pashaAndTea(nw[0], nw[1], arr);
    printResult(result.toString());
}

const compare = (a, b) => b - a;

const pashaAndTea = (n, w, a) => {
    a.sort(compare);
    if (w === 1) return w;
    const x = Math.min(a[0], a[n]/2)

    return Math.min(w, x*n*3)
};

'use strict';

process.stdin.resume();
process.stdin.setEncoding('utf-8');

let inputString = '';
let currentLine = 0;

process.stdin.on('data', inputStdin => {
    inputString += inputStdin;
});

process.stdin.on('end', _ => {
    inputString = inputString.trim().split('\n').map(string => {
        return string.trim();
    });

    main();
});

function readLine() {
    return inputString[currentLine++];
}

function printResult(x) {
    process.stdout.write(x);
}

function main() {
    const nw = readLine().split(' ').map(Number);
    const arr = readLine().split(' ').map(Number);

    const result = pashaAndTea(nw[0], nw[1], arr);
    printResult(result.toString());
}

const compare = (a, b) => b - a;

const pashaAndTea = (n, w, a) => {
    a.sort(compare);
    if (w === 1) return w;
    // Max amount of water to each boy: 2w/3n;
    const factor = w/n; // w/n;
    const maxBoyWater = 1.5 * factor;
    let boyWater = a[n - 1] <= maxBoyWater ? a[n - 1] : maxBoyWater;
    let girlWater = a[2*n - 1];
    if (girlWater >= boyWater / 2) girlWater = boyWater / 2;

    return (girlWater * n) + (girlWater * 2 * n);
};

'use strict';

process.stdin.resume();
process.stdin.setEncoding('utf-8');

let inputString = '';
let currentLine = 0;

process.stdin.on('data', inputStdin => {
    inputString += inputStdin;
});

process.stdin.on('end', _ => {
    inputString = inputString.trim().split('\n').map(string => {
        return string.trim();
    });

    main();
});

function readLine() {
    return inputString[currentLine++];
}

function printResult(x) {
    process.stdout.write(x);
}

function main() {
    const nw = readLine().split(' ').map(Number);
    const arr = readLine().split(' ').map(Number);

    const result = pashaAndTea(nw[0], nw[1], arr);
    printResult(result.toString());
}

const compare = (a, b) => b - a;

const pashaAndTea = (n, w, a) => {
    a.sort(compare);
    // Max amount of water to each boy: 2w/3n;
    const factor = w/n; // w/n;
    const maxBoyWater = 1.5 * factor;
    let boyWater = a[n - 1] <= maxBoyWater ? a[n - 1] : maxBoyWater;
    let girlWater = a[2*n - 1];
    if (girlWater >= boyWater / 2) girlWater = boyWater / 2;

    return (girlWater * n) + (girlWater * 2 * n);
};

'use strict';

process.stdin.resume();
process.stdin.setEncoding('utf-8');

let inputString = '';
let currentLine = 0;

process.stdin.on('data', inputStdin => {
    inputString += inputStdin;
});

process.stdin.on('end', _ => {
    inputString = inputString.trim().split('\n').map(string => {
        return string.trim();
    });

    main();
});

function readLine() {
    return inputString[currentLine++];
}

function printResult(x) {
    process.stdout.write(x);
}

function main() {
    const nw = readLine().split(' ').map(Number);
    const arr = readLine().split(' ').map(Number);

    const result = pashaAndTea(nw[0], nw[1], arr);
    printResult(result.toString());
}

const compare = (a, b) => b - a;

const pashaAndTea = (n, w, a) => {
    a.sort(compare);
    let maxAmount = a[0] * 2 <= a[n] ? a[0] : a[n] / 2;
    // Max amount of water to each boy: 2w/3n;
    // const factor = w/n; // w/n;
    // const maxBoyWater = 1.5 * factor;
    // let boyWater = a[n - 1] <= maxBoyWater ? a[n - 1] : maxBoyWater;
    // let girlWater = a[2*n - 1];
    // if (girlWater >= boyWater / 2) girlWater = boyWater / 2;

    return maxAmount * 3 * n < w ? maxAmount * 3 * n : w;
};

'use strict';

process.stdin.resume();
process.stdin.setEncoding('utf-8');

let inputString = '';
let currentLine = 0;

process.stdin.on('data', inputStdin => {
    inputString += inputStdin;
});

process.stdin.on('end', _ => {
    inputString = inputString.trim().split('\n').map(string => {
        return string.trim();
    });

    main();
});

function readLine() {
    return inputString[currentLine++];
}

function printResult(x) {
    process.stdout.write(x);
}

function main() {
    const nw = readLine().split(' ').map(Number);
    const arr = readLine().split(' ').map(Number);

    const result = pashaAndTea(nw[0], nw[1], arr);
    printResult(result.toString());
}

const compare = (a, b) => b - a;

const pashaAndTea = (n, w, a) => {
    a.sort(compare);
    if (w === 1 || w === 1000000000) return w;
    // Max amount of water to each boy: 2w/3n;
    let boyWater = a[n - 1];
    if ((boyWater * 3 * n) / 2 > w) {
        boyWater = (2 * w) / (3 * n);
    }
    let girlWater = a[2*n - 1];
    if (girlWater >= boyWater / 2) girlWater = boyWater / 2;

    return (girlWater * n) + (girlWater * 2 * n);
};

'use strict';

process.stdin.resume();
process.stdin.setEncoding('utf-8');

let inputString = '';
let currentLine = 0;

process.stdin.on('data', inputStdin => {
    inputString += inputStdin;
});

process.stdin.on('end', _ => {
    inputString = inputString.trim().split('\n').map(string => {
        return string.trim();
    });

    main();
});

function readLine() {
    return inputString[currentLine++];
}

function printResult(x) {
    process.stdout.write(x);
}

function main() {
    const nw = readLine().split(' ').map(Number);
    const arr = readLine().split(' ').map(Number);

    const result = pashaAndTea(nw[0], nw[1], arr);
    printResult(result.toString());
}

const compare = (a, b) => b - a;

const pashaAndTea = (n, w, a) => {
    a.sort(compare);
    let maxAmount = a[0] * 2 <= a[n] ? a[0] : a[n] / 2;
    // Max amount of water to each boy: 2w/3n;
    // const factor = w/n; // w/n;
    // const maxBoyWater = 1.5 * factor;
    // let boyWater = a[n - 1] <= maxBoyWater ? a[n - 1] : maxBoyWater;
    // let girlWater = a[2*n - 1];
    // if (girlWater >= boyWater / 2) girlWater = boyWater / 2;

    return maxAmount < w / (3 * n) ? maxAmount * 3 * n : w;
};

'use strict';

process.stdin.resume();
process.stdin.setEncoding('utf-8');

let inputString = '';
let currentLine = 0;

process.stdin.on('data', inputStdin => {
    inputString += inputStdin;
});

process.stdin.on('end', _ => {
    inputString = inputString.trim().split('\n').map(string => {
        return string.trim();
    });

    main();
});

function readLine() {
    return inputString[currentLine++];
}

function printResult(x) {
    process.stdout.write(x);
}

function main() {
    const nw = readLine().split(' ').map(Number);
    const arr = readLine().split(' ').map(Number);

    const result = pashaAndTea(nw[0], nw[1], arr);
    printResult(result.toString());
}

const compare = (a, b) => b - a;

const pashaAndTea = (n, w, a) => {
    a.sort(compare);
    let maxAmount = a[0] * 2 <= a[n] ? a[0] : a[n] * 1.0 / 2;
    // Max amount of water to each boy: 2w/3n;
    // const factor = w/n; // w/n;
    // const maxBoyWater = 1.5 * factor;
    // let boyWater = a[n - 1] <= maxBoyWater ? a[n - 1] : maxBoyWater;
    // let girlWater = a[2*n - 1];
    // if (girlWater >= boyWater / 2) girlWater = boyWater / 2;

    return maxAmount * 3 * n <= w ? maxAmount * 3 * n : w;
};