#include <bits/stdc++.h>
using namespace std;



int main(){
    long long int 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;
}