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

int main(){
	ll f0,f1,n; cin>>f0>>f1>>n;
	ll f2=f0^f1;
	if(n==0) cout<<f0<<endl;
	else if(n==1) cout<<f1<<endl;
	else {
		for(int i=2; i<=n; i++){
			f2=f0^f1;
			f0=f1; f1=f2;
		}
		cout<<f2<<endl;
	}
}