#include<cstdio>
#include <iostream>
#include<algorithm>
#include<string>
#include<queue>
#include<vector>
#include<functional>
#include<cmath>
#include<map>
#include<stack>
#include<set>
#include<numeric>

using namespace std;
typedef long long ll;
typedef pair<ll, ll> Pr;

ll F0, F1, N;

int main()
{
	cin >> F0 >> F1 >> N;
	if (N == 2) printf("%lld\n",F0^F1);
	else if (N % 2 == 0)cout << F1 << endl;
	else cout << F0 << endl;

	return	0;
}