.
                                     F
                            r      r e       r
                          e        e F         e
                        e           re           e
                        F            e             F
                        r          F    r          r
                        e         e     e          e
                         e         F    r         e
                           F        e e          F
                             r        F          r
                               e      r       e
                                       e
                                       e