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

int main()
{
long long F0;
long long F1;
long long N;

	cin >> F0;
	cin >> F1;
	cin >> N;

	switch( N % 3 )
	{
	case 0:
		cout << F0 << endl;

		return 0;
	case 1:
		cout << F1 << endl;

		return 0;
	case 2:
		cout << ( F0 ^ F1 ) << endl;

		return 0;
	}
}