import 'dart:math' as math;

sealed class Shape {
  double calculateArea();
}

class Square implements Shape {
  final double length;
  Square(this.length);
  double calculateArea() => length * length;
}

class Circle implements Shape {
  final double radius;
  Circle(this.radius);
  double calculateArea() => math.pi * radius * radius;
}

double calculateArea(Shape shape) => switch (shape) {
      Square(length: var l) => l * l,
      Circle(radius: var r) => math.pi * r * r
    };

main() {}

expect(expected, actual) {}