using System;

public class Program

{

    public static void Main()

    {

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

        try 

        {

            int num= int.Parse(Console.ReadLine());

            if(num<0)

                throw new ArgumentException("Invalid number.");

            Console.WriteLine(Math.Sqrt(num));

        }

        catch(ArgumentException ex)

        {

            Console.WriteLine(ex.Message);

        }

        finally

        { 

            Console.WriteLine("Good bye.");

        }

    }

​