import java.util.concurrent.*;
import java.util.concurrent.locks.*;

// ME among As.
// ME between Bs and Cs.
// ME between As and Cs.
// Priority to As.

class Monitor {

   Lock lock = new ReentrantLock();
   Condition ...

   ...

   Monitor() {
      ...
   }

   public void Aentry() {
      lock.lock();
      ...
      lock.unlock();
   }

   public void Aexit() {
      lock.lock();
      ...
      lock.unlock();
   }

   public void Bentry() {
      lock.lock();
      ...
      lock.unlock();
   }

   public void Bexit() {
      lock.lock();
      ...
      lock.unlock();
   }

   public void Centry() {
      lock.lock();
      ...
      lock.unlock();
   }

   public void Cexit() {
      lock.lock();
      ...
      lock.unlock();
   }
}