using System;

class Ring

{

    private double r1;

    private double r2;

    public Ring(double r1, double r2)

    {

        this.r1=r1;

        this.r2=r2;

    }

    public bool Correct()

    {

        return r1>r2&&r1>0&&r2>0;

    }

    public double Area()

    {

        return Math.PI *(r1 *r1-r2*r2);

    }

    public double LengthRing()

    {

        return 2*Math.PI*r1+2*Math.PI*r2;

    }

    public string MyRing()

    {

        if (Correct())

        {

            return $"Ring with radii {r1}, {r2}\n" +

                   $"Ring area: {Area():F3}\n" +

                   $"Total perimeter: {LengthRing():F3}";

        }

        else

        {

            return $"Ring with radii {r1}, {r2} does not exist.";

        }

    }

}

class Program

{

    static void Main()

    {

        try

        {

            Console.Write("Enter outer radius (r1): ");

            double r1 = double.Parse(Console.ReadLine());

            Console.Write("Enter inner radius (r2): ");

            double r2 = double.Parse(Console.ReadLine());

            Ring ring = new Ring(r1, r2);

            Console.WriteLine(ring.MyRing());

        }

        catch (Exception ex)

        {

            Console.WriteLine("Error: " + ex.Message);

        }

    }

}