#include <bits/stdc++.h>

using namespace std;

#define REP(i,a,b) for(int i=a;i<(int)b;i++)
#define rep(i,n) REP(i,0,n)

void bit_print(int x) {
  vector<int> b;
  while(x > 0) {
    b.push_back(x & 1);
    x >>= 1;
  }
  reverse(b.begin(), b.end());
  rep(i, b.size()) {
    cout << b[i];
  }cout << endl;
}

int main() {
  
  long long f0, f1, f2, N; cin >> f0 >> f1 >> N;
  f2 = f0 ^ f1;
  long long fn;
  if(N % 3 == 0) { fn = f0; }
  if(N % 3 == 1) { fn = f1; }
  if(N % 3 == 2) { fn = f2; }
  cout << fn << endl;
  
  return 0;
}