import java.io.*;
import java.util.Scanner;

class Main
{
	public static void main (String[] args) throws java.lang.Exception
	{
		Scanner in = new Scanner(System.in);
		long n = in.nextLong();
		long x = 1;
		long k = 1;
		long s = 1;
		while (s<n) {
			k++;
			x = x*2 + k;
			s = s + x;
		}
		System.out.print(k);
	}
}