/* -*- coding: utf-8 -*-
 *
 * 64.cc: No.64 XORフィボナッチ数列 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

/* typedef */

typedef long long ll;

/* global variables */

/* subroutines */

/* main */

// F2 = F1 ^ F0
// F3 = F2 ^ F1 = (F1 ^ F0) ^ F1 = F0
// F4 = F3 ^ F2 = (F2 ^ F1) ^ F2 = F1
// Fn = Fn-1 ^ Fn-2 = (Fn-2 ^ Fn-3) ^ Fn-2 = Fn-3

int main() {
  ll f[3], n;
  cin >> f[0] >> f[1] >> n;
  f[2] = f[1] ^ f[0];

  printf("%lld\n", f[n % 3]);
  return 0;
}