using Templates.Observer;
class Client {

  public static void Main(){
     Subject subj = new Subject();
     Observer o1 = new Observer(subj),
              o2 = new Observer(subj),
              o3 = new Observer(subj);

     subj.Attach(o1);  // o1 subscribes to updates from subj
     subj.Attach(o2);  // o2 subscribes to updates from subj

     subj.Notify();    // Following some state changes in subj
                       // notify observers
  }
}