Write a spell-checking program.
The program should read a list of valid words, one word on each line;
then a blank line; then a list of words to check, one word on each line.
It should print out each word that is not in the list of valid words.
Exception: It should not print a word that contains an uppercase letter.

You may assume that each word has at most 20 characters,
and that there are at most 100000 valid words.

For example, if the user types
   a
   aardvark
   is
   test
   the
   then

   This
   is
   aa
   test
then your program will print
   aa