#include <iostream>
using namespace std;
int main()
{
	int n,nn = 0,ans = 0;
	cin >> n;
	while (true)
	{
		ans += n;
		nn += n;
		n = nn / 3;
		nn -= n * 3;
		if (n == 0)
			break;
	}
	cout << ans;
	return 0;
}
//容易理解的写法