#include <iostream>

using namespace std;

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

	cin >> F0 >> F1 >> N;
	switch(  N % 3  ) {
	case 0:
		cout << F0 << endl;
		break;
	case 1:
		cout << F1 << endl;
		break;
	case 2:
		cout << (F1^F0) << endl;
		break;
	}

	return 0;
}