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.Scanner;

/*
 * @author Tanzim Ibn Patowary
 * Created  May 2, 2020 9:30:19 PM
 */
public class P492A {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner mScanner = new Scanner(System.in);
		int n = mScanner.nextInt();
		long a = 0;
		while (a * (a + 1) * (a + 2) <= 6 * n) {
			++a;
		}
		System.out.println(--a);
		
	}

}
