벌집

#include <iostream>
using namespace std;

int main()
{
	int room = 1, i = 0;
	int N;

	cin >> N;

	while (1)
	{
		room = room + 6 * i;

		if (N <= room)
		{
			cout << i + 1 << '\n';
			break;
		}
		else
			i++;
	}

	return 0;
}