static void Main(string[] args)
{
// Make a Rectangle.
Rectangle r = new Rectangle(15, 4);
Console.WriteLine(r.ToString());
r.Draw();
// Convert r into a Square,
// based on the height of the Rectangle.
Square s = (Square)r;
Console.WriteLine(s.ToString());
s.Draw();
Console.ReadLine();
// Implicit cast OK!
Square s3 = new Square();
s3.Length = 7;
Rectangle rect2 = s3;
Console.WriteLine("rect2 = {0}", rect2);
}