def memoize(f):
    answers = {}  # answers[args] = f(*args) 
    
    def wrapper(*args):
        if args not in answers:
            answers[args] = f(*args)
        return answers[args]

    return wrapper

@memoize
def binomial(n, k):
    if k==0 or k==n:
        return 1
    else: 
        return binomial(n-1, k) + binomial(n-1, k-1)

print(binomial(7, 5))