enter:
  i word   to insert word
  f word   to find word
  p        to print all
  x        to exit
> i the
the inserted
> i quick
quick inserted
> i brown
brown inserted
> i fox
fox inserted
> i jumped
jumped inserted
> i over
over inserted
> i the 
the inserted
> i lazy
lazy inserted
> i dogs
dogs inserted
> p
(((()brown((()dogs())fox(()jumped((()lazy())over()))))quick(()the()))the())
> x
$ a.out
enter:
  i word   to insert word
  f word   to find word
  p        to print all
  x        to exit
> i one
one inserted
> i two
two inserted
> i three
three inserted
> i four
four inserted
> p
((()four())one((()three())two()))
> x