1. Problem model is not clear: whether train from station 1, after reaching station N, continues then moving in the opposite direction (station N -> station 1), or "disappears" after?
2. Another bug in statement: "You may assume that train stops at each station are instant." and "it takes one second to board a train". How these two statements relate to each other? If train stop is instant, how tourist can board it the whole 1 second???

Answers:
1. No, it "disappears" (which is very different from the real world)
2. This stupid statement is just to show that the tourist should stay on the station during 1 minute, i.e. he cannot leave on the same train he reached the station with

Edited by author 01.07.2014 00:38