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

typedef long long ll;

signed main(){
  ll f[ 3 ], N;
  cin >> f[ 0 ] >> f[ 1 ] >> N;
  f[ 2 ] = f[ 0 ] ^ f[ 1 ];
  cout << f[ N % 3 ] << endl;
  return 0;
}