using System;

using System.Text;

using System.Collections;

public class Program

{

    public static void Main()

    {

        var input = "aabcccccccd";

        var hash = new Hashtable();

        for (var i = 0; i < input.Length; i++){

            if (hash.ContainsKey(input[i])){

                hash[input[i]] = (int)hash[input[i]] + 1;

            }

            else

            {

                hash.Add(input[i], 1);

            }

        }

​

        var str = new StringBuilder();

        foreach (var key in hash.Keys){

            str.Append(String.Format("{0}{1}", key, hash[key]));

        }

        if (str.Length > input.Length) {    

            Console.WriteLine(input);

        }

        else {

            Console.WriteLine(str);

        }

    }

}