from __future__ import division


def power(x, n):
    if x == 0:
        return "x can't be zero."
    if n == 0:
        return 1
    if n > 0:
        return x * power(x, n - 1)
    if n < 0:
        return 1 / power(x, -n)


print power(3, 3)
print power(2, -4)
print power(2, 0)
print power(0, -2)