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.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintStream;

/*492A - Vanya and Cubes*/
public class Codeforces492A {
	public static void main(String[] args) throws java.lang.Exception {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		PrintStream out = new PrintStream(new BufferedOutputStream(System.out));		
		int n = Integer.parseInt(in.readLine());
		int t = 0;
		int c = 0;
		int posible = 0;
		for (int i = 1; i <= 10_000; i++){
		  c += i;
		  t += c;
		  if (n >= t)
		    posible = i;
		  else
		    break;
		}
		System.out.println(posible);
	}
}