class Incrementer extends Thread {
   String name;
   Counter c;
   
   Incrementer(String name, Counter q){
      this.c = q;
      this.name = name;
      System.out.println("Incrementer " + name + " created");
   }

   public void run() {
      while(true){
         c.increment();
         System.out.println(name + " incremented the counter to " + c.counter);
         try {
            Thread.sleep(10);
         } catch (InterruptedException e) {return;}
      }
   }
}

class Decrementer extends Thread {
   String name;
   Counter c;
  
   Decrementer(String name, Counter q){
      this.c = q;
      this.name = name;
      System.out.println("Incrementer " + name + " created");
   }

   public void run() {
      while(true) {
         c.decrement();
         System.out.println(name + " decremented the counter to " + c.counter);
         try {
            Thread.sleep(10);
         } catch (InterruptedException e) {return;}
      }
   }
} 

      
class Counter {
   int counter;

   public Counter(int i) {
      counter = i;
   }

   public synchronized void increment() {
      try {
         while (counter >= 10) wait();
      } catch (InterruptedException e) {return;}
      counter++;
      notifyAll();
   }

      public synchronized void decrement() {
      try {
         while (counter <= 0) wait();
      } catch (InterruptedException e) {return;}
      counter--;
      notifyAll();
   }


   public static void main(String[] args) {
      Counter c = new Counter(0);
      new Incrementer("x", c).start();
      new Incrementer("y", c).start();
      new Decrementer("z", c).start();
      new Decrementer("w", c).start();
   }
}