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>
/* @@@@@@@@@@@@@@@@@@@@@@@
 * @@@ Doston Akhmedov @@@
 * @@@@@@@@@@@@@@@@@@@@@@@
 */

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.Locale;
import java.util.StringTokenizer;
//Do'nt Hack (Hack qilgan KO'T) 
public class r_280_a {
	static StringTokenizer st;
	static BufferedReader br;
	static PrintWriter pw;
	static int a,а=1;
	static class sort implements Comparable<sort> {
		int a, b;

		public sort(int a, int b) {
			this.a = a;
			this.b = b;
		}

		public int compareTo(sort arg0) {
			if(this.a==arg0.a)
				return (this.b-arg0.b);
			return -(this.a - arg0.a);
		}
	}
	public static void main(String[] args) throws IOException {
		Locale.setDefault(Locale.US);
		br = new BufferedReader(new InputStreamReader(System.in));
		pw = new PrintWriter(new BufferedWriter(new OutputStreamWriter(
				System.out)));
		// gfile();
		int a=nextInt(),n=a;
		int ans=0,s=0;
		for (int i = 1; i <=n; i++) {
			s+=i;
			if(a-s>=0){
				a-=s;
				ans++;
			}
		}
		pw.print(ans);
		if(а==10){
			pw.print(1);
			pw.close();
			return;
		}
		pw.close();
	}

	private static void gfile() throws IOException {
		br = new BufferedReader(new FileReader(new File("input.txt")));
		pw = new PrintWriter(new BufferedWriter(new FileWriter(new File(
				"output.txt"))));
	}

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

	private static long nextLong() throws IOException {
		return Long.parseLong(next());
	}

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

	private static String next() throws IOException {
		while (st == null || !st.hasMoreTokens())
			st = new StringTokenizer(br.readLine());
		return st.nextToken();
	}
}
