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>
import java.util.*;

public class VanyaCubes492A
{
    public static void main(String[] args) 
    {
        // Set up scanner
        Scanner sc = new Scanner(System.in); 
        // System.out.println("Enter n");
        int n = sc.nextInt();
        
        if (n==1)
        {
            System.out.println(1);
            return;
        }
        
        int sum = 1; 
        int nexttoadd = 2;
        int nextlevel = 3;
        int answer = 1;
        while (sum <= n)
        {
            sum += nextlevel;
            answer++;
            nexttoadd++;
            nextlevel += nexttoadd;
        }
        System.out.println(answer-1);
    }
}
        
            
            
            
        
        