#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;

ll N, F[3];

int main() {
  cin >> F[0] >> F[1] >> N;
  F[2] = F[0] ^ F[1];
  cout << F[int(N % 3)] << endl;
  return 0;
}