fix bug on calculating best of each lanuage
fix bug on calculating best of each lanuage

--HG--
branch : algo

cafe-grader-team/cafe-grader-web,jittat/cafe-grader-web,nattee/cafe-grader-web,cafe-grader-team/cafe-grader-web,cafe-grader-team/cafe-grader-web,nattee/cafe-grader-web,nattee/cafe-grader-web,jittat/cafe-grader-web,cafe-grader-team/cafe-grader-web,nattee/cafe-grader-web