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;

public class blarg {
	public static String[] qwerty = { "qwertyuiop", "asdfghjkl;", "zxcvbnm,./" };

	public static void main(String[] Args) {

		Scanner sc = new Scanner(System.in);
		long ans = 0;
		int n = sc.nextInt();
		long cur = 0;
		for (int k = 0; k < n; k++){
			cur += k + 1;
			ans += cur;
			if (ans > n){
				System.out.println(k);
				return;
			}
		}
		System.out.println(n);
	}

	public static boolean isp(int x) {
		boolean isp = true;
		if (x < 2)
			return false;
		for (int k = 2; k * k <= x; k++) {
			if (x % k == 0)
				return false;
		}
		return true;
	}
}
