.
                                   M
                          a      a s       a
                        s         t u         s
                       t          r b           t
                      u         a    t          u
                      r         e     M         r
                      b         a     s          b
                       a         t     u         a
                        t          r   b         t
                          e         a          e
                               •     t       •
                                     e