using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        String[] str=new String[] {"aaa.txt","aaa.pdf","aaa.TXT","aaa.xml","aaa.PDf"};

        var dict= new Dictionary<string,int>();

        foreach(var item in str)

        {

            String temp="";

           for(int i=0;i<item.Length;i++)

           {

              if(item[i]=='.')

               {

                  int j=i+1;

                  while(j<item.Length)

                  {

                   temp=temp+item[j];

                     j++;

                  }

                  break;

               }

           }

            if(dict.ContainsKey(temp.ToLower()))

              {

                 int val=dict[temp.ToLower()];

                 dict.Remove(temp.ToLower());

                 dict.Add(temp.ToLower(),val+1);

              }

            else

            { dict.Add(temp.ToLower(),1);

            }

        }

        foreach(var key in dict.Keys)

        {

            Console.WriteLine(dict[key] +" with " + key + " extensions ");

        }

    }

}