using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

         double n=double.Parse(Console.ReadLine());

        double s=n/2;

        double t=0;

        while(s!=t){

            t=s;

            s=((n/t)+t)/2;

        }

        Console.WriteLine(s);

    }

}