s5e6

def factorial(n):
    f = 1
    for i in range(2, n+1):
        f= f * i
    return(f)
def binom_prob(p, n, k):
    return(factorial(n)//(factorial(k)*factorial(n-k)))*(p**k)*((1-p)**(n-k))
print(binom_prob(0.5, 3, 3))