ProgrammingChallenges/modular_exponentiation.py

import math
import sys

def mod_exp(x, y, m):
    k = x % m
    results = {}
    return exp_m(results, k, y, m)

def exp_m(results, k, y, m):
    if y in results:
        return results[y]
    else:
        if k == 1:
            ret = 1
        elif y == 0:
            ret = 1
        elif y == 1:
            ret = k
        else:
            h = y // 2
            ret = (exp_m(results, k, h, m) % m * exp_m(results, k, y - h, m) % m) % m
        results[y] = ret
        return ret

line = sys.stdin.readline().split()
x = int(line[0])
y = int(line[1])
m = int(line[2])

print(mod_exp(x, y, m))