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>
/*
 *In the name of Allah the Most Merciful.
 * Author
 * Md. Toufiqul Islam
 * Dept. Of CSE
 * Ahsanullah University Of Science And Technology
 */

				
//package CodeForces;

import java.io.DataInputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Scanner;

public class R280A {
   
    public static void main(String[] arg){
    	Scanner sc = new Scanner(System.in);
    	
    	int n = sc.nextInt();
    	int i;
    	int sum=0;
    	for( i=1;sum<=n;i++){
    		int temp =0;
    		for(int j=1;j<=i;j++){
    			temp +=j;
    		}
    		sum+=temp;
    		if(sum>n){
    			System.out.println(i-1);
    			break;
    		}
    		
    	}
    	
    }
	
}
