The question asks if a trip can be made successfully, but it leaves out the definition of successfully. In an interview, I would ask the following questions (heck, I want the following questions answered by anyone before I even continue on this problems):

- Would the idea be to complete a circuit and keep the cost below 1 unit per distance?
- Can there be negative costs (so we can earn money)?
- How big can the number of stations be?

The last two questions can be easily deduced from the online judge if one has patients. But the first question is essential to this problem.

Does anyone have insight?