private static void ExplicitCasts() {
var r = new Rectangle(5, 7);
Console.WriteLine(r.ToString());
r.Draw();
Console.WriteLine();
var s = (Square) r;
Console.WriteLine(s.ToString());
s.Draw();
Console.WriteLine();
s = (Square) 3;
Console.WriteLine(s.ToString());
s.Draw();
Console.WriteLine();
}
