背景

航空公司的货运飞机往返于各个国家和货物分理中心之间，分理中心的货物运送到各个国家，再将各个国家发出的货物送到分理中心。



分理中心非常庞大，每个国家都有一个自己的货运站，每个货运站有两个平台用于堆放货物。其中 A 平台用于堆放运送到该国的货物，而 B 平台堆放着其它国家的货物。各个国家的货运站排成一个环形。

（详细见内部文档）-Background Airlines cargo flights to and from various countries and goods in the sub-Li centers, sub-arguments centered delivery of goods to various countries, and then sent to various countries of the goods issued by Sub-Center. Sub-Li center is very large, each country has its own cargo terminal, each terminal has two platforms used to stack cargo. Where A platform for stacking goods shipped to the country, while the B platform, goods piled up in other countries. Each country' s air cargo terminals arranged in a ring. (For details see the internal document)