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