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

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

	while (N)
	{
		F[0] ^= F[1];
		swap(F[0], F[1]);
		--N;
	}

	cout << F[0] << endl;
	
	return 0;
}