using System;

using System.Collections.Generic;

public class Program

{

    public static int a = 1;

    public static void Main()

    {

        var sequence = GenerateSequence();

        a = 2;

        foreach(var num in sequence)    

            Console.WriteLine(num);

    }

    public static IEnumerable<int> GenerateSequence()

    {

        yield return a;

        yield return 3;

    }   

}