You are a parcel courier in an old twelve-storey building with two slow lifts.

Collect up to three parcels at the post office. The deadlines start when you leave, so pick a good route. Deliver each parcel to the right door, then go back for more. Late parcels pay less.

Both lifts take 3 seconds per floor. The doors are manual: pull, push and close them yourself. Sometimes a lift gets stuck. No lift? Take the stairs. In the lift, keys 0–9 pick a floor.