#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, n;
  cin >> a >> b >> n;
  vector<long long int> f(n+1);
  f[0] = a;
  f[1] = b;
  for(int i=2; i<n+1; i++){
    f[i] = f[i-1] ^ f[i-2];
  }
  cout << f[n] << endl;
  return 0;
}