#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <iomanip>
#include <functional>
#include <cmath>
using namespace std;
#define lli long long int
lli a, b;

lli fib(lli n) {
	if (n == 0)	return a;
	if (n == 1) return b;
	return fib(n - 1) ^ fib(n - 2);
}

int main() {
	lli n, x;
	cin >> a >> b >> n;
	cout << fib(n) << endl;
	return 0;
}