static void Main(string[] args)
{
Circle aCircle = new Circle();
aCircle.radius = Convert.ToDouble(Console.ReadLine());
Console.WriteLine(aCircle.ShowDiameter(aCircle.radius));
Console.WriteLine(aCircle.ShowPerimeter(aCircle.radius));
Console.WriteLine(aCircle.ShowArea(aCircle.radius));
Console.ReadKey();
}