p = 4/5
n = 4


def binom(k, n, p):
    res = 1
    a = 1
    for i in range(1, n+1):
        a *= i
    b = 1
    for i in range(1, n-k+1):
        b *= i
    c = 1
    for i in range(1, k+1):
        c *= i
    return a/b/c * p**k * (1-p)**(n-k)


def prob(k):
    return binom(k, n, p)


if __name__ == '__main__':
    result = prob(3) + prob(4)
    print('%.3f' % result)

    result = prob(0) + prob(1)
    print('%.3f' % result)