//#define _USE_MATH_DEFINES	//M_PI
#include <iostream>			//std::cout, std::cin
//#include <string>			//std::string
#include <vector>			//std::vector
//#include <valarray>			//std::valarray	数値のみの一次配列
//#include <algorithm>		//std::sort
//#include <time.h>			//localtime_s
//#include <cstdlib>			//abs
//#include <cmath>			//abs, std::pow, sqrt, sin, cos,
//#include <fstream>			//std::ifstream
//#include <iomanip>			//std::setprecision
//#include <random>			//std::random(C++11)
//#include <numeric>			//std::accumulate

int main(void) {

	
	//test用
	//std::ifstream in("test.txt");
	//std::cin.rdbuf(in.rdbuf());

	std::vector<unsigned long long> F(2);
	unsigned long long N;
	std::cin >> F[0] >> F[1] >> N;

	for (int i = 0; i < N; i++) {
		F.push_back(F[i+1] ^ F[i]);
	}

	std::cout << F[N] << std::endl;

}