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.*;
import java.lang.reflect.Array;
import java.util.*;

public class Main {
    Random q = new Random(System.currentTimeMillis());
    int ox[];
    void qsort(int l, int r) {
        if (l < r) {
            int x = ox[q.nextInt(r - l + 1) + l];
            int i = l, j = r;
            while (i <= j) {
                while (ox[i] < x) i++;
                while (ox[j] > x) j--;
                if (i <= j) {
                    int t = ox[i];
                    ox[i] = ox[j];
                    ox[j] = t;
                    i++;
                    j--;
                }
            }
            qsort(l, j);
            qsort(i, r);
        }
    }

    public void solve() throws IOException {
        // write your code here
        int x = nextInt ();
        ArrayList<Integer> sum = new ArrayList<> ();
        sum.add (1);
        for(int i = 2; i < 142; i++){
            sum.add ((i * (i + 1))/2 + sum.get (i - 2));
        }
        int i = 0;
        while(sum.get (i) <= x) i++;
        out.print (i);

        out.close ();
    }

    BufferedReader br;
    StringTokenizer sc;
    PrintWriter out;

    public String nextToken() throws IOException {
        while (sc == null || !sc.hasMoreTokens ()) {
            try {
                sc = new StringTokenizer (br.readLine ());
            } catch (Exception e) {
                return null;
            }
        }
        return sc.nextToken ();
    }

    public int nextInt() throws IOException {
        return Integer.parseInt (nextToken ());
    }

    public double nextDouble() throws IOException {
        return Double.parseDouble (nextToken ());
    }

    public long nextLong() throws IOException {
        return Long.parseLong (nextToken ());
    }

    public static void main(String[] args) throws IOException {
        Locale.setDefault (Locale.US);
        new Main ().run ();
    }

    public void run() {
        try {
            br = new BufferedReader (new InputStreamReader (System.in));
            out = new PrintWriter (System.out);

            solve ();

            out.close ();
        } catch (IOException e) {
            e.printStackTrace ();
            System.exit (1);
        }
    }
}