#include <iostream>
#include <vector>
#include <cstdio>
#include <sstream>
#include <map>
#include <string>
#include <algorithm>
#include <queue>
#include <cmath>

using namespace std;


int main(){
	long long F[2];
	long long N;
	cin >> F[0] >> F[1] >> N;
	if(N%3LL == 0){
		cout << F[0] << endl;
	}else if(N%3LL == 1){
		cout << F[1] << endl;
	}else{
		cout << (F[0] ^ F[1]) << endl;
	}
	return 0;
}