using System;

​

namespace Problem 

{

    internal interface IShape

    {

        void Render();

    }

    internal class Circle : IShape

    {

        public double Radius { get; init; }

​

        public Circle(double radius)

        {

            Radius = radius;

        }

​

        public void Render()

        {

            Console.WriteLine("Rendering circle");

        }

    }

    internal class Rectangle : IShape

    {

        public double Width { get; init; }

​

        public double Height { get; init; }

​

        public Rectangle(double width, double height)

        {

            Width = width;

            Height = height;

        }

​

        public void Render()

        {

            Console.WriteLine("Rendering rectangle");

        }

    }

    internal class ShapeCalculator

    {

        public void CalculateArea(IShape shape)

        {

            if(shape is Circle circle)

            {

                Console.WriteLine(3.14 * circle.Radius * circle.Radius);

            }

            else if(shape is Rectangle rect)

            {

                Console.WriteLine(rect.Width * rect.Height);

            }

        }

    }

}

​

namespace Solution 

{

    internal interface IShape

    {

        void Render();

        void CalculateArea();

    }

    internal class Circle : IShape

    {

        public double Radius { get; init; }

​

        public Circle(double radius)

        {

            Radius = radius;

        }

​

        public void Render()

        {

            Console.WriteLine("Rendering circle");

        }

​

        public void CalculateArea()

        {

            Console.WriteLine(3.14 * this.Radius * this.Radius);

        }

    }

    internal class Rectangle : IShape

    {

        public double Width { get; init; }

​

        public double Height { get; init; }

​

        public Rectangle(double width, double height)

        {

            Width = width;

            Height = height;

        }

​

        public void Render()

        {

            Console.WriteLine("Rendering rectangle");

        }

​

        public void CalculateArea()

        {

            Console.WriteLine(this.Width * this.Height);

        }

    }

    internal class ShapeCalculator

    {

        public void CalculateArea(IShape shape)

        {

            shape.CalculateArea();

        }

    }

​

}

public class Program

{

    public static void Main()

    {

        var circle = new Solution.Circle(10);

        var shapeCalculator = new Solution.ShapeCalculator();

        shapeCalculator.CalculateArea(circle);

    }

}