.
                                   P
                             e   e a    e
                           a     c h       a
                         c       p e         c
                        h         ac          h
                      p           h              p
                     e             p               e
                    a              e                 a
                  p                a                  p
                 e                c  h                 e
                a                p     e                 a
               c                a        c                 c
               h               h        p                 h
                p                e      a                 p
                 e                  c h                  e
                    a                p                 a
                       c              e              c
                             h       a        h
                                       c
                                       h