#include <bits/stdc++.h>
#define rep(i, a) for (int i = 0; i < (a); i++)
#define rep2(i, a, b) for (int i = (a); i < (b); i++)
#define repr(i, a) for (int i = (a) - 1; i >= 0; i--)
#define repr2(i, a, b) for (int i = (b) - 1; i >= (a); i--)
using namespace std;
typedef long long ll;
const ll inf = 1e9;
const ll mod = 1e9 + 7;

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;
}