using System;
using System.Collections;
using System.Collections.Generic;

namespace ConsoleApp1
{
    
    class Program
    {
        static IEnumerable<string> AddAB(int Count)
        {
            string str = "h";
            for (int i = 0 ; i < Count; i++)
            {
                yield return str;
                str += "a";
            }
            Console.WriteLine("");
            for (int i = 0 ; i < Count; i++)
            {
                Console.WriteLine("before yoeld return "+str);
                yield return str;
                str += "b";
            }
        }
        static void Main(string[] args)
        {
            foreach (var str in AddAB(3))
            {
                Console.WriteLine(str);
            }
        }
    }
}