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 Hartha
 */
public class JavaApplication52 {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        Scanner sin = new Scanner(System.in);
        int n = sin.nextInt(), sum = 0 , temp = 0;
        for(int i= 1 ; ;i++)
        {
            temp += i;
            sum += temp;
            if(sum == n)
            {
                System.out.println(i);
                return;
            }
            if(sum > n)
            {
                System.out.println(i-1);
                return;
            }
        }
    }
    
}