Maybe it's only me who is of this opinion, but the statement of the problem is really equivocal. The expressions "If Leonid is wrong in his assumptions" and "Leonid assumes that the work experience of each pilot is in the range from 1 to 50 years" obviously led me to the misunderstanding of the problem itself, as I supposed that if the graph is disconnected the answer would be -1, because Leonid might be wrong in his assumptions in case if the difference in ages between pilots from two different connected components exceeds 50 years. Therefore it would be better to say "It is known that the work experience of each pilot is in range from 1 to 50 years" as it makes people understand that this is a required restriction.

I would be very grateful if authors avoided such tricky and equivocal expressions in their statements. Thank you for the time spent in order to look through this post.