Suppose there are three elevators, A, B, C, B and C. At present, elevator A 1~6, elevator B 7 ~1~ and elevator C 12~ 16 stay at different floors, and a prompt is given at the bottom. To save time.

Then there are many people coming and going on special floors, and the flow of people is obviously higher than other floors, such as 7-8 floors.

Then take elevator A 1~6, elevator B 7~8 and elevator C 9~ 16. Of course, the specific situation depends on the specific situation.