Three spaces is the answer. Male sex, female sex and mixed sex.
I noticed a big venue near us that for quite a while had the male symbol only on the gents and a fecking gallery of options on the ladies has quietly had it changed to traditional ladies and gents symbols. They have a kept a notice saying 'use the one that best fits your' Yadda Yadda Yadda but I wonder if they're doing a step change and will equally quietly lose that?
There's another venue that recently built mixed sex loos. What happens is everyone queues together - but volunteer ladies stand there bellowing THE URINALS ARE OVER THERE BEHIND THE SCREEN so poor chaps who need a poo are publicly embarrassed ....