#define _USE_MATH_DEFINES

#include <iostream>		//cin, cout
#include <vector>		//vector
#include <algorithm>	//sort,min,max,count
#include <string>		//string,getline, to_string
#include <cstdlib>		//abs(int)
#include <utility>		//swap, pair
#include <deque>		//deque
#include <climits>		//INT_MAX
#include <bitset>		//bitset
#include <cmath>		//sqrt, ceil. M_PI, pow, sin
#include <ios>			//fixed
#include <iomanip>		//setprecision
#include <sstream>		//stringstream
#include <numeric>		//gcd, assumlate
#include <random>		//randam_device
#include <limits>		//numeric_limits

using namespace std;
constexpr long long int D_MOD = 1000000007;

int main() {

	long long int F0, F1, N;
	cin >> F0 >> F1 >> N;

	long long int F2 = F1 ^ F0;

	if (N == 0) {
		cout << F0 << endl;
	}
	else if (N == 1) {
		cout << F1 << endl;
	}
	else if (N == 2) {
		cout << F2 << endl;
	}
	else {
		switch (N % 3) {
		case 2:cout << F2 << endl; break;
		case 1:cout << F1 << endl; break;
		case 0:cout << F0 << endl; break;
		}
	}

	return 0;

}