#include<iostream>
using namespace std;
#define ll long long

int main()
{
	ll F0, F1, N;
	cin >> F0 >> F1 >> N;

	ll F2 = F0^F1;

	if (N % 3 == 0) cout << F0 << endl;
	else if (N % 3 == 1) cout << F1 << endl;
	else cout << F2 << endl;

	return 0;
}