.
                                      B
                             o     o  m     o
                          m       b  B         m
                        b             B              b
                       B              o                B
                      o               m                 o
                     m               b                  m
                     b            B      o               b
                      B           m     b              B
                       o           B      o             o
                         m         m  b           m
                            b          B           b
                                        o
                                        m
                                         b