#include <bits/stdc++.h>

using namespace std;

#define rep(i, n) for(int i = 0; i < (int)n; ++i)
#define FOR(i, a, b) for(int i = a; i < (int)b; ++i)
#define rrep(i, n) for(int i = ((int)n - 1); i >= 0; --i)

using ll = long long;
using ld = long double;

const int Inf = 1e9;
const double EPS = 1e-9;
const int MOD = 1e9 + 7;

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(0);
    ll a, b, n;
    cin >> a >> b >> n;
    if (n % 3 == 0) cout << a << endl;
    else if (n % 3 == 1) cout << b << endl;
    else cout << (a ^ b) << endl;
    
    return 0;
}