//No.64 XORフィボナッチ数列
#include <iostream>
#include <vector>
using namespace std;

signed main(){
    long long f0 , f1 , n;
    cin >> f0 >> f1 >> n;
    if( n % 3 == 0) cout << f0 << endl;
    else if( n % 3 == 1) cout << f1 << endl;
    else if( n % 3 == 2) cout << (f0^f1) << endl;
}