.
                                         F
                                r      r e       r
                              e        s h          e
                             s          F r           s
                           h            e               h
                           F          s     h           F
                            r         F      r           r
                             e        e      s          e
                              s     ­    h   F         s
                                 h      r  e       h
                                           h