#include<iostream>
#include<algorithm>
#include<bitset>
using namespace std;
int main() {
  long long f0,f1,n,f2;
  cin >> f0 >> f1 >> n;
  f2=f1^f0;
  if(n%3==0) {
      cout << f0 << endl;
  }
  else if(n%3==1) {
      cout << f1 << endl;
  }
  else {
      cout << f2 << endl;
  }
}