def binom(n, k):
    if k == 0 or n == k:
        return 1
    elif k < 0 or n < k:
        return 0
    else:
        return binom(n-1, k) + binom(n-1, k-1)



def binom2(n, k):
    if k < 0 or n < k:
        return 0
    else:
        b = [1]
        for j in range(n):
            c = [1] + [b[i] + b[i+1] for i in range(0, j)] + [1]
            b = c
        return b[k]