def facto(n):

    f = 1

    for i in range(1,n+1):

        f = f*i

    return f

​

​

def binom(n,p,k):

    return (1.0*facto(n))/(facto(k)*facto(n-k))*(p**k)*((1-p)**(n-k))

​

​

def binomSup(n,p,k):

    s = 0

    for i in range(k+1,n+1):

        s = s+binom(n,p,i)

    return s

​

def risque(n,p,a):

    k = 0

    while binomSup(n,p,k) > a and k < n:

        k = k+1

    return k

​

print risque(100,0.8,0.05)

​