#include <bits/stdc++.h>
using namespace std;

int main()
{
	int64_t f0, f1, n;
	cin >> f0 >> f1 >> n;
	
	if(n % 3 == 0) cout << f0 << endl;
	else if(n % 3 == 1) cout << f1 << endl;
	else cout << (f0 ^ f1) << endl;
	return 0;
}