#include <bits/stdc++.h>
#define rep(i, a, n) for (int i = a; i < n; i++)
#define repr(i, a, n) for (int i = n - 1; i >= a; i--)
using namespace std;
using ll = long long;
using P = pair<int, int>;
template <typename T> void chmin(T &a, T b) { a = min(a, b); }
template <typename T> void chmax(T &a, T b) { a = max(a, b); }

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);

  ll f0, f1, n;
  cin >> f0 >> f1 >> n;

  if (n % 3 == 2)
    cout << (f0 ^ f1) << endl;
  else if (n % 3 == 1)
    cout << f1 << endl;
  else
    cout << f0 << endl;
}