#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <cmath>
#include <string>
#include <vector>
#include <algorithm>
#include <queue>
#include <map>
#include <functional>
#include <set>
#include <numeric>
#include <stack>
#include <utility>
//#include "util.h"

using namespace std;
typedef long long lint;
typedef pair<lint, lint> Pii;

int main()
{
	lint F[3], N;
	cin >> F[0] >> F[1] >> N;
	F[2] = F[0] ^ F[1];
	cout << F[N % 3] << endl;

	return 0;
}