.
                                   C
                          r     r   e     r
                       e        a   m       e
                     a          C   r           a
                   m              e              m
                  C                a                C
                  r                m                r
                  e             C      r             e
                   a            e      a            a
                    m           m  C           m
                      C            r               C
                        r           e             r
                          e         a           e
                            a       m       a
                               m   C    m
                                      r
                                      e
                                      a
                                     m