说明：  这是一个关于电梯模拟的问题，非常值得我们去思考，去研究。
(We encourage you to simulate a lift system with 100 stops (100 floors). We assume every customer takes 1 second to enter the lift and 1 second to leave. The lift’s occupation space is 13 people with no weight limit. It takes 10 seconds for the lift to travel between two nearby floors without discrimination for going up or going down. )