using System;

public class Circle

{

    public static void Main()

    {

        String inputRadius;

        String inputOption;

        double radius;

        int option;

        Console.Write("Enter Radius: ");

        inputRadius = Console.ReadLine();

        if (double.TryParse (inputRadius, out radius) == true) 

        {

            Console.WriteLine("Select Option");

            Console.WriteLine("1. Area of the Circle \n2. Circumference of the Circle");

            Console.Write("Enter Option: ");

            inputOption = Console.ReadLine();

            if (radius <= 0) 

            {

                Console.WriteLine("Zero or Negative value is not allowed.");

            }

            else

            {

                if (Int32.TryParse(inputOption, out option) == true)

                {

                    if (option == 1) 

                    {

                        double area = 3.1416 * (radius * radius);

                        Console.WriteLine("The area of a circle is {0:#,0.0000}", area);

                    }

                    else if (option == 2) 

                    {

                        double circumference = 2 * 3.1416 * radius;

                        Console.WriteLine("The circumference of a circle is {0:#,0.0000}", circumference);

                    }

                    else 

                    {

                        Console.WriteLine("Option must be 1 or 2 only. Please input a valid option.");

                    }

                }

            }

        } 

        else

        {

            Console.WriteLine("Invalid input.");

        }

    }

}