using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        var names=new string[]{"Alfred", "Bob", "Albert", "Benny", "Dave", "Charlie"};

        var letters=names.Select(n=>n.First());

        Console.WriteLine(String.Join(",",letters.ToArray()));

        var orderedLetters=letters.OrderBy(l=>l);

        Console.WriteLine(String.Join(",",orderedLetters.ToArray()));

        var distLetters=orderedLetters.Distinct();

        Console.WriteLine(String.Join(",",distLetters.ToArray()));                      

    }

}