using System;

public class Program

{

      public static string Encode(string txt)

      {

          string result = string.Empty;

          foreach (char ch in txt)

          {

              // "tku" will be our delimiter

              result += Convert.ToString((int)ch, 10) + "tku";;

          }

          result = result.Replace("0", "dos");

          result = result.Replace("1", "vso");

          result = result.Replace("2", "otw");

          result = result.Replace("3", "foa");

          result = result.Replace("4", "bae");

          result = result.Replace("5", "xgd");

          result = result.Replace("6", "ymt");

          result = result.Replace("7", "ksx");

          result = result.Replace("8", "wte");

          result = result.Replace("9", "rom");

          return result;

        }

        public static string Decode(string txt)

        {

            string result = txt;

            result = result.Replace("dos", "0");

            result = result.Replace("vso", "1");

            result = result.Replace("otw", "2");

            result = result.Replace("foa", "3");

            result = result.Replace("bae", "4");

            result = result.Replace("xgd", "5");

            result = result.Replace("ymt", "6");

            result = result.Replace("ksx", "7");

            result = result.Replace("wte", "8");

            result = result.Replace("rom", "9");

            // "tku" will be converted to spaces

            result = result.Replace("tku", " ");

            string result2 = string.Empty;

            // and we split over them

            foreach(var res in result.Split(' '))

            {

              if(!String.IsNullOrWhiteSpace(res))

              {

                result2 += ((char)Int32.Parse(res)).ToString();

              }

            }           

            return result2;

        }

    public static void Main()

    {

        var res = Encode("test encoding");

        var res2 = Decode(res);

        Console.WriteLine(res);

        Console.WriteLine(res2);

    }

}