using System;

using System.Collections;

​

public class Program

{

        public static void Main()

        {

         string Message = "Codility we test coders";

        int n = 20;

            Console.WriteLine(returnString(Message,n));

        }

     private static string returnString(string Message,int n)

     {

         string result = "";

         if(Message.Length == 0){Console.WriteLine("Empty string");}

         if(n==0){return Message;}

         result = Message.Substring(0,n);

         int k = 0;

         for(int i=result.Length-1; i>0; i--)

         {

            if(result[i].ToString() != " ")

            {

                k++;

                Console.WriteLine(result[i] + ":"+ k);

            }

             else

             {

                 break;

             }

         }

         return result.Substring(0,result.Length-k);

         //return result;

     }

}