static void Main(string[] args)
{
// Клиентский код.
var subject = new Subject(); //магазин
var observerFirst = new FirstClient(); //Наблюдатель первый
subject.Attach(observerFirst);
var observerSecond = new SecondClient();//Наблюдатель второй
subject.Attach(observerSecond);
var observerThird = new ThirdClient();
subject.Attach(observerThird);
subject.NewspapperLogic();
subject.NewspapperLogic();
subject.JournalLogic();
subject.Detach(observerSecond);
subject.NewspapperLogic();
}