using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        string result = RemoveDuplicate("abaaaaaaccccccccd");

        Console.WriteLine(result);

    }

    public static string RemoveDuplicate(string input)

    {

        Console.WriteLine(input);

         if(input.Length <= 1)

            return input;

        if(input[0] == input[1])

            return RemoveDuplicate(input.Substring(1));

        else

            return input[0] + RemoveDuplicate(input.Substring(1));

    }

}