.

                                      L
                      ­        o     o  v       o
                           v        e  L          v
                         e            o               e
                        L             v                L
                       o              e                 o
                       v           L     o             v
                       e          v       e             e
                        L          L     o             L
                         o           v  e             o
                           v           L            v
                               e       o        e
                                        v  
          ­                              e