12 pax and 2 lavs in F. The lavs are in front of the divider curtain C/F. The FAs usually are strict in keeping the lowly masses in C out of our lavs. And, there is a sticker on the lav door indicating "For First Class passengers only" or, if the sticker is gone, I've even seen hand-written notes taped to the lav doors.

So, if you are in F, chances are good you won't have to deal with C pee or poop!