static void Main()
{
Circle circle = new Circle(5);
Console.WriteLine("I am a circle. " +
"My perimeter is {0:f2}. My surface is {1:f2}.",
circle.CalcPerimeter(), circle.CalcSurface());
Rectangle rect = new Rectangle(2, 3.5);
Console.WriteLine("I am a rectangle. " +
"My perimeter is {0:f2}. My surface is {1:f2}.",
rect.CalcPerimeter(), rect.CalcSurface());
}