.
                                       M
                            o         oo         o
                          o            n             o
                        n             M               n
                       M              o                M
                      o                o                   o
                      o             n    M               o
                       n            o      o              n
                       M           n    M            M
                         o            o   o             o
                           o            n              o
                                n      M         n
                                         o
                                         o
                                         n