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.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;

public class Cf {

	public static void main(String[] args) throws Exception {
		// TODO Auto-generated method stub
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in,
                "ISO-8859-1"));
        PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out,
                "ISO-8859-1"));
        String line=in.readLine();
        String[] lineTokens=line.trim().split("\\s+");
        int n=Integer.parseInt(lineTokens[0]);
        for(int i=1;i<=50;i++){
        	if(i*(i+1)*(i+2)/6>n){
        		System.out.println(i-1);
        		break;
        	}
        }
        
		
		out.flush();
		in.close();
		System.exit(0);
	}

}