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

int main() {
  ll f0, f1, n;
  cin >> f0 >> f1 >> n;
  if (n % 3 == 0) {
	  cout << f0 << endl;
	}
  else if (n % 3 == 2) {
	  cout << (f0 ^ f1) << endl;
	} else {
	  cout << f1 << endl;
	}
  return 0;
}