#include <iostream>
#include <vector>
using namespace std;
int main() {
	vector<unsigned long int> F;
	unsigned long int F0, F1,N,Temp;
	cin >> F0 >> F1 >> N;
	F.push_back(F0);F.push_back(F1);
	for (int i = 2; i <= N;i++) {
		Temp = F[i - 1] ^ F[i - 2];
		F.push_back(Temp);
	}
	cout << F[N] << endl;
	return 0;
}