.
                                 G
                           r    r e   r
                       e        e k       e
                     e           G            e
                   k             r               k
                  G              e               G
                 r                e                 r
                e           ­      k                  e
                e             G     r                e
                k            e        e              k
        ­        G            k       G             G
                 r             r      e             r
                   e             e  k             e
                      e            G           e
                           k        r       k
                                     e
                                     e
                                     k