#include <vector>
#include <iostream>
#include <string>
#include <sstream>
#include <algorithm>
#include <utility>
#include <map>

using namespace std;
typedef long long ll;
typedef pair<ll,ll> P;

int main(){
	ll f0,f1,N;
	cin >> f0 >> f1 >> N;
	if(N == 0){ cout << f0 << endl; return 0;}
	if(N == 1){ cout << f1 << endl; return 0;}
	vector<ll> f(1000,0);	
	f[0] = f0; f[1] = f1;

	map<P,ll> mp;
	for(int i = 2;i <= N;i++){
		if(mp.count(P(f[i-1],f[i-2]))){
			N %= (i - mp[P(f[i-1],f[i-2])]);	
		}
		f[i] = f[i-1] ^ f[i-2];
		mp[P(f[i-1],f[i-2])] = i;
	}

	cout << f[N] << endl;

	return 0;
}