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.util.*;

public class RCC {
	
	Scanner in;
	static PrintWriter out;
	
	static class Scanner  {
		
		StreamTokenizer in;
		
		Scanner (InputStream is) {
			in = new StreamTokenizer(new BufferedReader(new InputStreamReader(is)));
		}
		
		int nextInt() {
			try {
				in.nextToken();
				return (int)in.nval;
			} catch (IOException e) {
				throw new Error();
			}
		}
	}
	
		
	void solve() {
		int n = in.nextInt();
		int used = 0;
		int take = 1;
		int h = 0;
		while (used + take <= n) {
			used += take;
			h++;
			take += h+1;
		}
		out.println(h);
	}
	
	static void asserT(boolean e) {
		if (!e) {
			throw new Error();
		}
	}
	
	public void run() {
		in = new Scanner(System.in);
		out = new PrintWriter(System.out);
		try {
			solve();
		} finally {
			out.close();
		}
	}
	
	public static void main(String[] args) {
		new RCC().run();
	}
}