#include <iostream>
#include <vector>
using namespace std;
int main() {
	vector<long long> F;
	long long F0, F1, N;
	cin >> F0 >> F1 >> N;
	F.push_back(F0);F.push_back(F1);F.push_back(F1^F0);
	cout << F[N % 3] << endl;
	return 0;
}