public class Point
{
public int x, y;
public Point(int x, int y) {
this.x = x;
this.y = y;
}
}
public class Point3D: Point
{
public int z;
public Point3D(int x, int y, int z): base(x, y) {
this.z = z;
}
}
public class BaseClasses{
public static void Main()
{
Point a = new Point(10, 20);
Point b = new Point3D(10, 20, 30);
}
}