using System;
using static System.Console;
using static System.Math;
using static System.String;

class Program
{
   static void Main()
   {
      Write("Enter a circle's radius: ");
      var input = ReadLine();
      if (!IsNullOrEmpty(input) && double.TryParse(input, out var radius)) {
         var c = new Circle(radius);
         
         string s = "\nInformation about the circle:\n";
         s = s + Format("   Radius: {0:N2}\n", c.Radius);
         s = s + Format("   Diameter: {0:N2}\n", c.Diameter);
         s = s + Format("   Circumference: {0:N2}\n", c.Circumference);
         s = s + Format("   Area: {0:N2}\n", c.Area);
         WriteLine(s);
      }
      else {
         WriteLine("Invalid input...");
      }
   }
}

public class Circle
{
   public Circle(double radius)
   {
      Radius = radius;
   }

   public double Radius { get; set; }

   public double Diameter
   {
      get { return 2 * Radius; }
   }

   public double Circumference
   {
      get { return 2 * Radius * PI; }      
   }

   public double Area
   {
      get { return PI * Pow(Radius, 2); }
   }
}
// The example displays the following output:
//       Enter a circle's radius: 12.45
//       
//       Information about the circle:
//          Radius: 12.45
//          Diameter: 24.90
//          Circumference: 78.23
//          Area: 486.95