abstract class Path {
  abstract boolean isOk();
}
 
class Fail extends Path {
  Fail() { }
  boolean isOk() { return false; }
}
 
class Success extends Path {
  Success() { }
  boolean isOk() { return true; }
}
 
class Right extends Path {
  Path rest;
  Right(Path rest) { this.rest = rest; }
  boolean isOk() { return true; }
}
 
class Left extends Path {
  Path rest;
  Left(Path rest) { this.rest = rest; }
  boolean isOk() { return true; }
}

// ----------------------------------------

abstract class Door {
  abstract Path escapePath(Person p);
} 

class Into extends Door {
  Room next;
  Into(Room next) {
    this.next = next;
  }
  Path escapePath(Person p) {
    return this.next.escapePath(p);
  }
}

class Escape extends Door {
  String name;
  Escape(String name) {
    this.name = name;
  }
  Path escapePath(Person p) {
    if (p.isDest(this.name))
      return new Success();
    else
      return new Fail();
  }
}

class Short extends Door {
   Room next;
   double height;
   Short(Room next, double height) {
     this.next = next;
     this.height = height;
   }
   Path escapePath(Person p) {
     if (p.height <= this.height)
       return this.next.escapePath(p);
     else
       return new Fail();
   }
}


class Room {
  Door left;
  Door right;
  Room(Door left, Door right) {
   this.left = left;
   this.right = right;
  }
  Path escapePath(Person p) {
   Path lp = this.left.escapePath(p);
   if (lp.isOk())
     return new Left(lp);
   else {
     Path rp = this.right.escapePath(p);
     if (rp.isOk())
       return new Right(rp);
     else
       return new Fail();
    }
  }
}

class Person {
  String dest;
  double height;
  Person(String dest, double height) {
    this.dest = dest;
    this.height = height;
  }
  boolean isDest(String s) {
    return this.dest.equals(s);
  }
}

// The Factory class helps in writing tests:
//  new Factory().Example().escapePath(new Person("mars", 1))
class Factory {
  Factory() { }
  Room Example() {
    Door meadow = new Escape("meadow");
    Door street = new Escape("street");
    Room ms = new Room(meadow, street);
    Room planets = new Room(new Escape("mars"),
                            new Escape("venus"));
    return new Room(new Into(ms),
                    new Short(planets, 1));
  }
}