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.InputStream;
import java.util.Scanner;


public class R280 {

	public static void main(String[] args) {
		System.out.println(vanyaAndCubes(System.in));
	}
	
	public static String vanyaAndCubes(InputStream in) {
		Scanner input = new Scanner(in);
		int n = input.nextInt();
		input.close();
		int num = 1;
		int i = 1;
		while (num <= n) {
			num += (i+1)*(i+2)/2;
			if (num <= n) {
				i++;
			}			
		}
		return i+"" ;
	}
}
