Clash of clan - double letter

I am having troubles with the last test of the “double letter” clash :

The program:
Your program must find all the “double letter” words. A word is “double letter” if it contains at least two identical letters next to each other.

Letter case does not matter, so A == a.

The tricky one is just “balloon” and we have to output 1.
I am pretty sure I missed something but I have no clue of what it is.

balloon contains 2 “double letter” but is only one word (i.e. one “double letter” word). That’s why the expected output is 1.

Thanks a lot.
I can’t believe I could not find that myself.

Would you mind closing this topic plz?