.
                                      F
                       ­        r    r e      r
                            e       e d        e
                          e         om          e
                         d         F  r       ­    d
                         o        e     e          o
                        m       d      o         m
                         F       m     F          F
                           r       r     e         r
                             e       e d        e
                                e     o       e
                                    d     d
                                       m