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>
/*
ID: yl5381
LANG: JAVA
TASK: lgame
*/

import java.io.*;
import java.util.*;

public class solve {
	public static void main(String[] args) throws IOException {
		Scanner f = new Scanner(System.in);

		int numCubes = Integer.parseInt(f.nextLine());

		int i  = 0;
		while (true) {
			if ((i * (i + 1) * (i + 2)) / 6 > numCubes) {
				System.out.println(i - 1);
				break;
			}
			i++;

		}

	}
}