#include<stdio.h>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <algorithm>
#include <sstream>
#include <iostream>
#include <string>

using namespace std;

int main() {
	
	long long f0,f1, N;

	cin >>f0 >>f1 >> N;
 
	if (N == 0) {
		cout << f0 << endl;
		return 0;
	}else if(N==1){
		cout << f1 << endl;
		return 0;
	}

	long long next;
	for (int i = 1; i < N; i++) {
		next = f1 ^ f0;
		f0 = f1;
		f1 = next;
	}

	cout << next << endl;

	return 0;
}