#include<bits/stdc++.h>
using namespace std;
int Fib(int a, int b, int n){
    if(n == 0) return a;
    if(n == 1) return b;
    return Fib(a, b, n-1) ^ Fib(a, b, n-2);
}
int main(){
    int F0, F1, N; cin >> F0 >> F1 >> N;
    cout << Fib(F0, F1, N) << endl;;
    return 0;
}