def reliability_calc(RACC, ACC):
    """
    Calculate reliability.

    :param RACC: random accuracy
    :type RACC : float
    :param ACC: accuracy
    :type ACC : float
    :return: reliability as float
    """
    try:
        result = (ACC - RACC) / (1 - RACC)
        return result
    except Exception:
        return 'None'
