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>
//package Codeforces.Div2A_280.Code1;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.StringTokenizer;

/*
 * some cheeky quote
 */

public class Main
{
    FastScanner in;
    PrintWriter out;

    public void solve() throws IOException
    {
        int sum = in.nextInt();
        int temp = 0;
        for (int i = 1; true; i++)
        {
            temp += sum(i);
            if (temp > sum)
            {
                System.out.println(i - 1);
                return;
            }
        }
    }

    public int sum(int n)
    {
        return n * (n + 1) / 2;
    }

    public void run()
    {
        try
        {
            in = new FastScanner();
            out = new PrintWriter(System.out);

            solve();

            out.close();
        } catch (IOException e)
        {
            e.printStackTrace();
        }
    }

    class FastScanner
    {
        BufferedReader br;
        StringTokenizer st;

        FastScanner()
        {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        String next()
        {
            while (st == null || !st.hasMoreTokens())
            {
                try
                {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e)
                {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt()
        {
            return Integer.parseInt(next());
        }
    }

    public static void main(String[] arg)
    {
        new Main().run();
    }
}

