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

using namespace std;

typedef long long ll;

#define MOD 1000000007

int main() {
  ll f0, f1, n;
  cin >> f0 >> f1 >> n;
  n %= 3;
  if (n == 0) {
    cout << f0 << endl;
  } else if (n == 1) {
    cout << f1 << endl;
  } else {
    cout << (f0 ^ f1) << endl;
  }
  return 0;
}