Vanya got n cubes. He decided to build a pyramid from them. Vanya wants to build the pyramid as follows: the top level of the pyramid must consist of 1 cube, the second level must consist of 1 + 2 = 3 cubes, the third level must have 1 + 2 + 3 = 6 cubes, and so on. Thus, the i-th level of the pyramid must have 1 + 2 + ... + (i - 1) + i cubes.

Vanya wants to know what is the maximum height of the pyramid that he can make using the given cubes.

Input

The first line contains integer n (1 ≤ n ≤ 104) — the number of cubes given to Vanya.

Output

Print the maximum possible height of the pyramid in the single line.

Examples

Input

1


Output

1


Input

25


Output

4

Note

Illustration to the second sample: 

<image>
/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */


/**
 *
 * @author Administrator
 */

import java.util.Scanner;


public class Vanya {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args)
    {
        // TODO code application logic here
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();
        
        
        int i=0;
       while(n>0)
        {
            i=i+1;
            n=n-(i*(i+1)/2) ;
            
        }
       if(n<0)
           i=i-1;
       
        
        
        
        System.out.println(i);
        
        
    }
}
