aaaaaaaaaaaaaaaaaaaaaaaaa
a                       a
a     b                 a
a                 *     a
a                       a
aaaaa     aaaaaaaa    aaaaaaaaaaaa
ccccc     c      a               a
c         c      a               a
c         c      a         a     a
c         ccccccca         a     a
c               ca         a     a
c               ca         a     a
c               caaaaaa    a     a
c       cccc    ccccccaaaaaa     a
c       cccc         ca          a
c                    cb          a
c                    ca          a
ccccccccccccccccccccccaaaaaaaaaaaa