.
                                     h
                            o      o r       o
                         r         s d'          r
                        s          o e             s
                       d'           u               d'
                       o             v               o
                       e          r      e           e
                        u         s      h          u
                         v         o     r          v
                          r         s    d'        r
                            e        o e        e
                                s      u      s
                                        v
                      ­                  r
                                        e
   ­                                     s