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.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.StringTokenizer;

public class A {

    public void solve() {
        int n = in.nextInt();
        int t = 0;
        int level = 0;
        while(t < n) {
            int sum = 0;
            level++;
            for (int i = 1; i <= level; i++)
                sum += i;
            t += sum;
        }
        if (t > n) level--;
        out.println(level);
    }

    String file = "";
    FastReader in;
    PrintWriter out;

    public void run() throws FileNotFoundException {
        if (file.length() == 0) {
            in = new FastReader();
            out = new PrintWriter(System.out);
        } else {
            in = new FastReader(file + ".in");
            out = new PrintWriter(new File(file+".out"));
        }
        solve();
        out.flush();
        out.close();
    }

    public static void main(String[] args) throws FileNotFoundException {
        new A().run();
    }

    class FastReader {

        BufferedReader bf;
        StringTokenizer st;

        public FastReader() {
            bf = new BufferedReader(new InputStreamReader(System.in));
        }

        public FastReader(String file) {
            try {
                bf = new BufferedReader(new FileReader(file));
            } catch (FileNotFoundException ex) {
            }
        }

        public String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(bf.readLine());
                } catch (IOException ex) {
                }
            }
            return st.nextToken();
        }

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

        public long nextLong() {
            return Long.parseLong(next());
        }
    }

}
