import math


def MCC_calc(TP, TN, FP, FN):
    """
    Calculate MCC (Matthews correlation coefficient).

    :param TP: true positive
    :type TP : int
    :param TN: true negative
    :type TN : int
    :param FP: false positive
    :type FP : int
    :param FN: false negative
    :type FN : int
    :return: MCC as float
    """
    try:
        result = (TP * TN - FP * FN) / \
            (math.sqrt((TP + FP) * (TP + FN) * (TN + FP) * (TN + FN)))
        return result
    except ZeroDivisionError:
        return "None"