#include <cstdio>
#include <iostream>
#include <string>
#include <vector>
#include <sstream>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <typeinfo>
#include <numeric>
#include <functional>
#include <unordered_map>
#include <bitset>


using namespace std;
using ll = long long;
using ull = unsigned long long;

const ll INF = 1e16;
const ll MOD = 1e9 + 7;

#define REP(i, n) for(ll i = 0; i < n; i++)





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