#include <iostream>
#include <vector>
#include <string>
#include <set>
#include <map>
#include <algorithm>
const int mod=1e9+7;
using LL=long long;
using std::cout;using std::endl;using std::cin;
using std::vector;using std::string;using std::set;using std::multiset;
using std::pair;using std::map;
using std::min;using std::max;
using std::make_pair;using std::swap;
std::ostream& operator<<(std::ostream& os,std::map<int,int>& obj){for(std::map<int,int>::iterator itr=obj.begin();itr!=obj.end();itr++){os<<itr->first<<"^"<<itr->second<<" ";}return os;}
std::ostream& operator<<(std::ostream& os,std::vector<std::map<int,int>>& obj){for(auto itr=obj.begin();itr!=obj.end();itr++){os<<*itr<<std::endl;}return os;}
std::ostream& operator<<(std::ostream& os,std::vector<int>& obj){for(auto itr=obj.begin();itr!=obj.end();itr++){os<<*itr<<" ";}return os;}
std::ostream& operator<<(std::ostream& os,std::vector<std::vector<int>>& obj){for(auto itr=obj.begin();itr!=obj.end();itr++){os<<*itr<<std::endl;}return os;}

namespace ndifix{
template<class T> void sort(T &v){std::sort(v.begin(),v.end());}

}


int main(){
  LL f0,f1,n;cin>>f0>>f1>>n;

  switch (n%3){
    case 0: cout<<f0<<endl;break;
    case 1: cout<<f1<<endl;break;
    case 2: cout<<(f0^f1)<<endl;break;
  }
  return 0;
}