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>
/**
 * Created by User on 10/13/2016.
 */
import java.util.Scanner;
public class towDarry {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        /*//int twod[][] = new int[2][2];
        //for(int i=0 ; i<2 ; i++)for(int j=0 ; j<2 ; twod[i][j++]=in.nextInt());
        //for(int i=0 ; i<2 ; i++,System.out.printf("\n"))for(int j=0 ; j<2 ; System.out.printf(twod[i][j++] + " "));
        int newd[][] = new int[2][];
        newd[0] = new int[1];
        newd[1] = new int[2];
        for(int i=0 ; i<2 ; i++)for(int j=0 ; j<i+1 ; newd[i][j++] = in.nextInt());
        for(int i=0 ; i<2 ; i++,System.out.printf("\n"))for(int j=0 ; j<i+1 ; System.out.printf(newd[i][j++] + " "));*/

        int n = in.nextInt(); int  i = 1 , sum = 0 , c = 0 ;
        while(sum < n)
        {
            sum += i ;
            if(sum > n)break;
            n -= sum ;c++ ;i++;
        }
        System.out.println(c);;

    }
};
