# -*- coding: utf-8 -*-


def make_xor_fib(F0, F1, N):
    a, b = F0, F1
    for _ in range(N):
        a, b = b, int(bin(a ^ b)[2:], 2)
    return a


if __name__ == '__main__':
    input_list = list(map(int, input().split()))
    F0, F1, N = input_list[0], input_list[1], input_list[2]
    print(make_xor_fib(F0, F1, N))