using System;

using System.Collections.Generic;

using System.Text;

public class Program

{

    public static void Main()

    {

 const string original = "aabbccddeefff";

            var compressed = CompressBetter(original);

            Console.WriteLine("Original  : {0}", original);

            Console.WriteLine("Compressed: {0}", compressed);

    }

​

​

        private static string CompressBetter(string str)

        {

​

            var sb = new StringBuilder();

            var last = str[0];

            var count = 1;

​

            for (var i = 1; i < str.Length; i++)

            {

                if (str[i] == last)

                {

                    count++;

                }

                else

                {

                    sb.Append(last);

                    sb.Append(count);

                    last = str[i];

                    count = 1;

                }

            }

            sb.Append(last);

            sb.Append(count);

if (sb.Length >= str.Length){

return str; 

}

            return sb.ToString();

        }

}