using System;

using System.Data;

using System.Data.DataSetExtensions;

using System.Linq;

public class Program

{

    public static void Main()

    {

        String input_txt = "A\n\nB\n\nB\nC\n\nC\nD\n\nA\n\nE";

        var distinctLines = input_txt.Split(Environment.NewLine.ToCharArray(), StringSplitOptions.None).Distinct().ToArray(); 

        Console.WriteLine(string.Join("\r\n", distinctLines));

    }

}