#include<iostream>
#include<algorithm>
#include<string>
using namespace std;
typedef long long int LL;
int main(){
    LL a[3];
    LL n;
    cin>>a[0]>>a[1];
    cin>>n;
    a[2]=a[0]^a[1];
    cout<<a[n%3]<<endl;
    return 0;
}