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 codeForcesTry;

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

public class A492_VanyaCubes implements Closeable{
	BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
	PrintWriter writer = new PrintWriter(System.out);
	StringTokenizer stringTokenizer;

	String next() throws IOException {
	    while (stringTokenizer == null || !stringTokenizer.hasMoreTokens()) {
	        stringTokenizer = new StringTokenizer(reader.readLine());
	    }
	    return stringTokenizer.nextToken();
	}

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

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

	long nextLong() throws IOException {
	    return Long.parseLong(next());
	}
	public void solve() throws IOException{
		int n=nextInt();
		int i=2,ans=1;
		n--;
		for(;;i++){
			if(n>=i*(i+1)/2){
				n=n-i*(i+1)/2;
				ans++;
			}
			else
				break;
		}
		System.out.println(ans);
	}
	public static void main(String args[]) throws IOException{ 
		try(A492_VanyaCubes c=new A492_VanyaCubes()){
		c.solve();
		}
	}
	public void close() throws IOException {
	    reader.close();
	    writer.close();
	}


}
