#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <list>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <algorithm>
#include <functional>
#include <limits>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <climits>
#include <complex>

using namespace std;

#define INF (INT_MAX/3)
#define PI (2*acos(0.0))
#define EPS (1e-8)

typedef long long ll;
typedef unsigned long long ull;

int main(){
    ios_base::sync_with_stdio(0);
    ull F0, F1, N;
    cin >> F0 >> F1 >> N;
    if(N % 3 == 0) cout << F0 << endl;
    else if(N % 3 == 1) cout << F1 << endl;
    else cout << (F0 ^ F1) << endl;
    return 0;
}