
a
ab
abc
abcd
abcde
abcdef
abcdefg
abcdefgh
       a
      ab
     abc
    abcd
   abcde
  abcdef
 abcdefg
abcdefgh

a
a b
a b  c
a b  c   d
a b  c   d    e
a b  c   d    e     f
a b  c   d    e     f      g
a b  c   d    e     f      g       h
                                   a
                                 a b
                              a b  c
                          a b  c   d
                     a b  c   d    e
               a b  c   d    e     f
        a b  c   d    e     f      g
a b  c   d    e     f      g       h
