import java.util.*;
import java.lang.*;
import java.io.*;
 
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		double h;
		Scanner sc = new Scanner(System.in);
    		h = sc.nextInt();
    		double p = Math.sqrt(2*h/9.8075);
    		System.out.printf("%.4f", p);
		sc.close();
	}
}