At first my algorithm spliced the string as:

   ["I", "don", "t"...]

And it gave incorrect result because in this case the word "less" became more scored.

After I added the symbol "'" (apostrophe) to the allowed characters for word, I completed this riddle.

But in description it stands clear that word consists of a sequence of letters or a single letter.

Am I missed something here?

Thanks in advance!