#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

int main(void) {
  ll a, b, c;
  cin >> a >> b >> c;
  
  if (c % 3 == 0) {
    cout << a << endl;
  } else if (c % 3 == 1) {
    cout << b << endl;
  } else {
    cout << (a ^ b) << endl;
  }

  return 0;
}