Elevator Calling Algorithm

For flyering the 3 in a row sets of elevators at SUTD

1. Push the up and down buttons to call two at once. Flyer one.
Easy.
2. Next flyer the other that came.
Easy.
3. Check what floor the third elevator is waiting on and take current elevator to that floor. Press the up and down buttons again to keep the current and the third elevator waiting. Flyer the third.
Less easy but satisfying.