#include <iostream>
#include <sstream>
#include <math.h>
#include <stack>
#include <set>
#include <algorithm>
#include <string>
#include <queue>
#include <stack>
#include <map>
#include <cstdio>
#include <vector>
using namespace std;

#define INF (1 << 30)
#define INFLL (1LL << 60)

int main() {
	long long f0,f1,n,x;
	cin >> f0 >> f1 >> n;
	if(n % 3 == 2) x = f0^f1;
	else if(n % 3 == 1) x = f1;
	else x = f0;
	cout << x << endl;
	return 0;
}