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.*;

public class for_test{
    public static void main(String[] args) throws IOException {
        new for_test().run();
    }


    StreamTokenizer in;
    PrintWriter out;

    int nextInt() throws IOException {
        in.nextToken();
        return (int) in.nval;
    }
    String nextString() throws IOException{
        in.nextToken();
        return in.sval;
    }
    char nextChar() throws IOException {
        in.nextToken();
        return (char) in.nval;
    }

    void run() throws IOException {
        in = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
        out = new PrintWriter(new OutputStreamWriter(System.out));
        solve();
        out.flush();
    }
    void solve() throws IOException {

        int n = nextInt();
        int i=0;
        int line=0;
        while(n>0){
            i++;
            line+=i;
            n-=line;
        }
        if(n<0){
            out.println(i-1);
        } else {
         out.println(i);
        }


    }
}