using System;

using System.Text;

using System.Linq;

using System.Collections.Generic;                   

public class Program

{

    static string extract(string original)        {

            List<char> characters = new List<char>();

            string unique = string.Empty;

            foreach (char letter in original.ToCharArray())

            {

                if (!characters.Contains(letter))

                {

                    characters.Add(letter);

                }

            }

            foreach (char letter in characters)

            {

                unique += letter;

            }

            return unique;

        }   

    public static void Main()

    {   

        //string input = "WWW.C-SHARPCORNER.COM";       

         string input = "aabcdeabc";        

         //string answer = new String(input.Distinct().ToArray());      

        string answer = extract(input);

        Console.WriteLine(answer);      

        string s = "AAABBBBBCCCCFFFFGGGGGDDDDJJJJJJ";       

        string newstr = String.Join("", s.Distinct());      

        Console.WriteLine(newstr); 

        /* for(int i=0; i<answer.Length; i++)

        {

            Console.Write(answer[i]+" ");

            int count=0;

            for(int j=0; j<input.Length; j++)

            {

                if(answer[i]==input[j])

                {

                    ++count;                    

                }

            }

            Console.Write(count+"\n");

        } */                        

        while (input.Length > 0)

            {

                Console.Write(input[0] + " : ");

                int count = 0;

                for (int j = 0; j < input.Length; j++)

                {

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

                    {

                        count++;

                    }

                }

                Console.WriteLine(count); 

                input = input.Replace(input[0].ToString(),string.Empty);               

            }  

    }

}