//#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());

	unsigned long long F0, F1, F2, N;
	std::cin >> F0 >> F1 >> N;

	if (N != 0) {
		for (int i = 0; i < N - 1; i++) {
			F2 = F0 ^ F1;
			F0 = F1;
			F1 = F2;
		}
		std::cout << F1 << std::endl;
	}
	else {
		std::cout << F0 << std::endl;
	}

}