#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstdlib>
#include<vector>
#include<map>
#include<queue>
#include<string>
#include<sstream>
#include<cmath>
using namespace std;


int main(){

  long long int a, b, c, n;
  cin >> a >> b >> n;
  c = a ^ b;

  if( n%3 == 0 ) cout << a << endl;
  else if( n%3 == 1 ) cout << b << endl;
  else cout << c << endl;

  return 0;
}