class Rectangle extends Shape {
  public {
    init(Int width, Int height) {
      this.width := width;
      this.height := height;
    }
    Int area() {
      return width * height;
    }
    Int perimeter() {
      return 2 * (width + height);
    }
  }
  protected {
    Int width;
    Int height;
  }
}
