[2292] 벌집

#include <iostream>
using namespace std;
int main(void)
{
	long n, range=1;
	int cnt = 1;
	cin >> n;
	while (1)
	{
		if (range >= n)
			break;
		range += (cnt++) * 6;
	}
	cout << cnt;
	return 0;
}