#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <cmath>
#include <iomanip>
#include <map>
using namespace std;
typedef long long LL;

int main(){
    LL 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;
}