模拟一个机场飞机降落和起飞的过程。内容：一个小飞机场有1条跑道，在天上有一个队列的飞机准备降落，地上有一队列的飞机准备起飞，当然必须等天上的飞机全部降落完后才能开始起飞。-Simulate a process of airport landing and take-off. Content: a small airport one runway, there is a queue in the sky of the plane to land, a queue for the plane ta