def modularExponential(base, power, mod): if power < 0: return -1 base %= mod result = 1 while power > 0: if power & 1: result = (result * base) % mod power = power >> 1 base = (base * base) % mod return result def main(): print(modularExponential(3, 200, 13)) if __name__ == '__main__': main()