# -*- coding: utf-8 -*-
"""
No.64 XORフィボナッチ数列
https://yukicoder.me/problems/no/64

"""
import sys
from sys import stdin
input = stdin.readline


def main(args):
    F0, F1, N = map(int, input().split())
    fibo = [F0, F1, F0^F1]
    print(fibo[N%3])


if __name__ == '__main__':
    main(sys.argv[1:])