#include <bits/stdc++.h>
#define rep(i, n) for(long long i = 0; i < (long long)n; i++)
#define ALL(v) (v).begin(), (v).end()
#define rALL(v) (v).rbegin(), (v).rend()
using namespace std;

using lint = long long;

int main() {
    lint f0, f1, n;
    cin >> f0 >> f1 >> n;
    lint ans = 0;
    rep(i, 62) {
        lint x = (f0 & (1LL << i) ? 1 : 0), y = (f1 & (1LL << i) ? 1 : 0);
        if (x == 0 && y == 1) {
            if (n % 3 != 0) {
                ans |= (1LL << i);
            }
        } else if (x == 1 && y == 0) {
            if (n % 3 != 1) {
                ans |= (1LL << i);
            }
        } else if (x == 1 && y == 1) {
            if (n % 3 != 2) {
                ans |= (1LL << i);
            }
        }
    }
    cout << ans << endl;
}