#define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES
#include <iostream>
#include <map>
#include <list>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <string>
#include <vector>
#include <algorithm>
#include <utility>
#include <queue>
#include <iomanip>
#define INF 1050000000

using namespace std;


int main(void)
{
	long long f0, f1, n;
	long long ans;

	cin >> f0 >> f1 >> n;

	if (n == 0) {
		cout << f0 << endl;
		return (0);
	}
	if (n == 1) {
		cout << f1 << endl;
		return (0);
	}
	for (int i = 2; i <= n; i++) {
		ans = f0 ^ f1;
		f0 = f1;
		f1 = ans;
	}
	 cout << ans << endl;

	 return (0);
}