-1 -1 1 1 -1 1 -1 1 1 0 0 1 1 1 1 2 2 1 1 0 0 0 1 0 0 0 -2 1 0 -1 0 1 -1 -1 -1 0 1 -1 0 P Q R c P Q R C c A c d A C l A C D C d l