.

                                      F
                            o      o  o      o
                          o        l  F          o
                         l            o              l
                       F             o               F
                      o              l                 o
                      o           F    o             o
                       l           o      l             l
                        F          F    o           F
                          o          o l           o
                            o          F         o
                                 l      o      l
                                        o
                                        l