#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int main() {
  vector<ll> f(3);
  ll n;
  cin >> f[0] >> f[1] >> n;
  f[2] = f[0] ^ f[1];
  ll ans = f[n % 3];
  cout << ans << '\n';
  return 0;
}