using System;
using System.Collections;

namespace yield_test
{
    class Program
    {
        static void Main(string[] args)
        {
            foreach (var number in GetNumbers())
            {
                Console.WriteLine(number);
            }
        }

        static IEnumerable GetNumbers()
        {
            yield return 1;
            yield return 2;
            yield return 3;
        }
    }
}