using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("---");

        Console.WriteLine(System.IO.Path.GetExtension("https://approved.net/thing/thing2.html"));

        Console.WriteLine(System.IO.Path.GetExtension("https://approved.net/thing/"));

        Console.WriteLine(System.IO.Path.GetExtension("https://approved.net/thing/thing2.png/"));

        Console.WriteLine(System.IO.Path.GetExtension("https://approved.net/thing/thing2.png"));

        Console.WriteLine(System.IO.Path.GetExtension("https://approved.net/thing/"));

        Console.WriteLine("---");

    }

}