import java.util.Scanner;
import java.util.InputMismatchException;

abstract class Shape {
	abstract double area();
	abstract void display();
}

class Rectangle extends Shape {
	double length, width;
	Rectangle(double len, double wid) {
		length = len;
		width = wid;
	}
	double area() {
		return length * width;
	}
	void display() {
		System.out.println("A rectangle with length " + length + " units and width " + width + " units has the area of " + area() + " square units.");
	}
}

class Circle extends Shape {
	double radius;
	Circle(double r) {
		radius = r;
	}
	double area() {
		return Math.PI * radius * radius;
	}
	void display() {
		System.out.println("A circle with radius " + radius + " units has the area of " + area() + " square units.");
	}
}

class Triangle extends Shape {
	double a, b, c;
	Triangle(double s1, double s2, double s3) {
		a = s1;
		b = s2;
		c = s3;
	}
	double perimeter() {
		return a + b + c;
	}
	double area() {
		var s = perimeter() / 2.0;
		return Math.sqrt(s * (s - a) * (s - b) * (s - c));
	}
	void display() {
		System.out.println("A triangle with side lengths " + a + " units, " + b + "units and " + c + " units has the area of " + area() + " square units.");
	}
}

class AbstractShapeCalculations {
    public static void main(String[] args) {
        try {
            Scanner sc = new Scanner(System.in);
            System.out.println("Calculate and display shapes\n");
            System.out.println("Rectangle");
            System.out.print("  Enter length: ");
            double length = sc.nextDouble();
            System.out.print("  Enter width: ");
            double width = sc.nextDouble();
            Shape s;
            s = new Rectangle(length, width);
            s.display();
            System.out.println("Circle");
            System.out.print("  Enter radius: ");
            double radius = sc.nextDouble();
            s = new Circle(radius);
            s.display();
            System.out.println("Triangle");
            System.out.print("  Enter three side lengths: ");
            double a = sc.nextDouble(), b = sc.nextDouble(), c = sc.nextDouble();
            s = new Triangle(a, b, c);
            s.display();
        } catch (InputMismatchException e) {
            System.err.println("Invalid numbers in input");
        }
    }
}