#include 
#include 
using namespace std;

class Subject {
    // 1. "independent" functionality
    vector < class Observer * > views; // 3. Coupled only to "interface"
    int value;
  public:
    void attach(Observer *obs) {
        views.push_back(obs);
    }
    void setVal(int val) {
        value = val;
        notify();
    }
    int getVal() {
        return value;
    }
    void notify();
};

class Observer {
    // 2. "dependent" functionality
    Subject *model;
    int denom;
  public:
    Observer(Subject *mod, int div) {
        model = mod;
        denom = div;
        // 4. Observers register themselves with the Subject
        model->attach(this);
    }
    virtual void update() = 0;
  protected:
    Subject *getSubject() {
        return model;
    }
    int getDivisor() {
        return denom;
    }
};

void Subject::notify() {
  // 5. Publisher broadcasts
  for (int i = 0; i < views.size(); i++)
    views[i]->update();
}

class DivObserver: public Observer {
  public:
    DivObserver(Subject *mod, int div): Observer(mod, div){}
    void update() {
        // 6. "Pull" information of interest
        int v = getSubject()->getVal(), d = getDivisor();
        cout