acm pkuThere is a famous railway station in PopPush City.Country there is iThere is a famous railway station in PopPush City.Country there is incredibly hilly.The station was built in last century.Unfortunately,funds were extremely limited that time.It was possible to establish only a surface track.Moreover,it turned out that the station could be only a dead-end one (see picture) and due to lack of available space it could have only one track.The loca

问题描述:

acm pkuThere is a famous railway station in PopPush City.Country there is i
There is a famous railway station in PopPush City.Country there is incredibly hilly.The station was built in last century.Unfortunately,funds were extremely limited that time.It was possible to establish only a surface track.Moreover,it turned out that the station could be only a dead-end one (see picture) and due to lack of available space it could have only one track.
The local tradition is that every train arriving from the direction A continues in the direction B with coaches reorganized in some way.Assume that the train arriving from the direction A has N

有一个PopPush市著名的铁路车站.国家有令人难以置信的丘陵.该站建于上个世纪.不幸的是,资金极为有限的时间.这是可能的建立只是一个表面的轨道.此外,事实证明,该站只能是死路一条之一(见照片),并由于缺乏可用它只能有一个轨道.
当地的传统是,每列车由A方向的重组在某种程度上与教练的方向B继续抵达.假设从A方向列车有N