Bon, à trois je pars à gauche, et toi à droite.
I wonder if this phrasing sounds good enough? Saying "à trois" rather than"sur trois"? Basically, I wanted to express the idea of "On my mark/count, three, two, one, go".
In German, for instance, you say "Okay, auf drei. Ich links, du rechts", with "auf" corresponding to "sur". In Italian, on the other hand, it would be "allora al mio tre", with "al" being interpreted as both "à" and "sur".
How do French speakers commonly express this idea? Would you use some other phrase?