#include <iostream>
#include <algorithm>
#include <cstring>
#include <climits>
typedef long long LL;
using namespace std;

int main()
{
	LL F[2], N, ans;
	cin >> F[0] >> F[1] >> N;

	switch (N % 3)
	{
	case 0:
		ans = F[0];
		break;
	case 1:
		ans = F[1];
		break;
	case 2:
		ans = F[0] ^ F[1];
		break;
	}
	cout << ans << endl;

	return 0;
}