#include <iostream> 
#include <string> 
#include <vector> 
#include <cmath> 
#include <algorithm> 
#include <cstdlib> 
#include <ctime> 
#include <cstdio> 
#include <functional> 
#include <set> 
#include <sstream> 
#include <cctype>

using namespace std; 


int 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 cout<<(f0^f1)<<endl;


	return 0;
}