class Shape
{
protected double area = 0.0d;
public virtual double Area() { return area; }
}
class Round : Shape
{
public Round(double r) { area = 3.14d * r * r; }
}
class Rect : Shape
{
public Rect(double x, double y) { area = x * y; }
}
void Main()
{
var rnd = new Round(1);
Console.WriteLine(rnd.Area());
var rect = new Rect(1, 1);
Console.WriteLine(rect.Area());
}