using System;

​

public class BaseClass

{

   protected int a=0;

​

   public void ChangeA()

   {

       a=5;

   }

}

​

public class SubClass : BaseClass

{

   public void PrintValue()

   {

       Console.Write(a);

   }

}

​

​

public class Program

{

    public static void Main()

    {

        var a = new SubClass();

        a.ChangeA();

        a.PrintValue();

    }

}