using System;

using System.Text.RegularExpressions;           

public class Program

{

    public static void Main()

    {

        string countries = "İstanbulAnkaraIzmirBursaKonya";

        string[] result =  Regex.Replace(countries, "(\\S)([A-Z][a-z])", "$1_$2")

        .Split(new char[] { '_' }, StringSplitOptions.RemoveEmptyEntries);

        foreach(var x in result)

            Console.WriteLine(x);

     }

}