.
                                  Cha  
                       ­ C        Cha        C
                     h           Cha            h
                    a              C            ­     a
                   C               h                  C
                   h               a                   h
                   a             C   h                a
                   C             a   C                C
                    h            h   a               h
                      a           C h               a
                        C           a              C
                           h        C           h
                              a      h       a
                                       a