import java.util.Scanner;

public class N508 {

	public static void main(String[] args)
	{
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		long r=Math.round(Math.sqrt(n/3));
		if(r<=0)
		{
			r+=100;
		}
		System.out.println(r);
	}
}