.
                                      C
                       ­      r       r i        r
                           i         me          i
                         m          C             m
                        e             r               e
                        C           i   m           C
                         r          e    C           r
                          i          r    i           i
                           m       e  C         m
                              e        r          e
           ­                      C     i       C
                                    r  m   r
                                       iei