.
                                     C
                               o   o m  o
                            m    p  l      m
               ­           p       e  x         p
                         l           C             l
                        e           u              e
                      x             n                x
                     C              t                  C
                    u        ­     C  o                 u
                   n             m   p                 n
                  t                l      e                   t
                 C                x     C                  C
                  o                u   n                   o
                  m                  t                     m
                    p                 C                   p
                       l               o                 l
                          e           m            e
                               x       p      x
                                        l
                                        e
                                        x