using System;

using System.Collections.Generic;

​

​

public class Program

{

    public static void Main()

    {

        //aabcccccaaa => a2b1c5a3

​

        string s="aabcccccaaa";

        string result="";

        //Dictionary<char,int> dict=new Dictionary<char,int>();

        Char[] chs=s.ToCharArray();

        int chlen=chs.Length, count=1;

​

        for(int i=1;i<=chlen-1;i++)

        {

            if(chs[i-1]==chs[i])

               {

                   count++;

               }

               else

               {

                   result+=chs[i-1];

                   result+=count;

                   count=1;

               }

        }

        result+=chs[chs.Length-1];

        result+=count;

        Console.WriteLine(result);

    }

}