def Cdf(_input_array, x):
    """
    Compute the CDF value of input samples using left tail computation
    Attributes:
        _input_array: list of data points
        x: current K value
    Return:  value of cdf
    """
    # left tail
    count = 0.0
    for vi in _input_array:
        if vi <= x:
            count += 1.0
    prob = count / len(_input_array)
    return prob