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

int main(){
	vector<long long int> f(2);
	long long int n;
	for(auto &a:f) cin >> a;
	cin >> n;
	long long int tmp;
	for(int i = 2; i <= n; i++){
		tmp = f[i - 1] ^ f[i - 2];
		f.push_back(tmp);
	}
	//	for(auto a:f) cout << a << endl;
	cout << f[n] << endl;
	return 0;
}