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.io.*;
import java.util.*;
import java.math.*;
import java.text.*;
public class Main
{
public static void main(String[] args)throws java.lang.Exception
{
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
PrintWriter out=new PrintWriter(System.out);
long i,n,cubes;



n=Long.parseLong(in.readLine());

i=0;
cubes=0;

do
{
++i;
cubes+=(i*(i+1))/2;

}while(cubes<=n);

out.println(i-1);


out.flush();
out.close();
}
} 