#include <iostream>
#include <string>
#include <vector>
#include <algorithm>

#define REP(i,k,n) for(int i=k;i<n;i++)
#define rep(i,n) for(int i=0;i<n;i++)

using namespace std;
typedef long long ll;

int main()
{
	ll f,f1,f2,n;
	cin >> f >> f1 >> n;

	if(n == 0) cout << f << endl;
	else if(n == 1) cout << f1 << endl;
	else
	{
		for(int i=2;i<=n;i++)
		{
			f2 = f ^ f1;

			f = f1;
			f1 = f2;
		}

		cout << f2 << endl;
	}
	
	return 0;
}