D-Dart

Dr.D has recently come to believe that a normal game of darts is boring and easy, so he invented his own version and called it D-Dart. First, Dr.D chooses a point on the wall and pins three dart rings to the wall at this point (since Dr.D has only one nail); it is only possible to pin a dart ring at a point that lies on its border. The exact position of this point is not important, since you ar