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.*;


public class vanyakubiki {
	public static void main (String args[]) {
		Scanner in = new Scanner (System.in);

		int n = in.nextInt();
		int sum = 0, summ = 0, count = 0;
		for (int i = 1; i <= 100001; i++) {
			sum += i;
			summ += sum;
			if (summ <= n) {
				count++;
			}
			else {
				break;
			}
		}
		System.out.println (count);
	}
}