#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <cctype>
#include <cmath>
#include <iostream>
#include <queue>
#include <list>
#include <map>
#include <numeric>
#include <set>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;


int main(){
  ll F0, F1, N;
  cin >> F0 >> F1 >> N;

  if(N==0){
    cout << F0 << endl;
    return 0;
  }
  if(N==1){
    cout << F1 << endl;
    return 0;
  }
  vector<ll> F;
  F.push_back(F0);
  F.push_back(F1);

  int M = 0;
  for(int i=2; ; i++){
    ll tmp = F[i-1] ^ F[i-2];
    F.push_back(tmp);
    if(F[0] == F[F.size()-2] && F[1] == F[F.size()-1]){
      M = i-1;
      break;
    }
  }
  cout << F[N%M] << endl;
  
  return 0;
}