#include <vector>
#include <queue>
#include <deque>
#include <stack>
#include <map>
#include <set>
#include <algorithm>
#include <functional>
#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <cctype>
#include <string>
#include <cstring>

using namespace std;

typedef long long ll;


int main() {
  ll f0, f1, n;
  cin >> f0 >> f1 >> n;
  ll a[] = {f0, f1, f0^f1};
  cout << a[n%3] << endl;
}