def mpy(m, n): if n == 0: return 0 return add(m, mpy(m, pred(n))) print(mpy(5, 4))

The function mpy takes two arguments m and n and multiplies them together by adding the first argument, m, to itself n number of times.

explanation 
    of the code: 
def pow(m, n):
    if n == 0:
        return 1
    return mpy(m, pow(m, pred(n)))
print(pow(5, 4))