You pick the shortest side....
It's pretty common (and good design) to have 2 runs fill the lift from either side. You take a look for the shortest line at the last pitch.
Pretty poor for the hill not have a corral.
(which brings me to my pet peeve: every hill wants to improve their upload capacity without buying new lifts. Train your lifties to manage the lines on busy days so that every chair goes up full. Viola! 30-50% more uploads! Pisses me off to pay big $$ for a lift ticket only to stand in a long line watching chair after chair go up with an empty seat or 2)