.

                                       alt
                                l      er       l
                             t         na         t
                            e          ti            e
        ­                   r         v    e          r
                           n       a       l         n
                           a        t       e         a
                            t          r  n           t
                             i           a            i
                               v        t          v
                                  e      i ­     e
                                         v
                                         e