It's not clear from problem statement that towers are numbered in lexicographical order of their records.

"Those arrays are sorted in ascending order."

I don't remember if this phrase was there or appeared as result of my previous post, but still it sounds strangely... Because one may think that it speks about internal arrays sorting, so what's the point writing them bottom-up then? :) Also, ascending sorting does not state criteria of descent/ascension (lexicographity).

I'd write it like this: "List of those arrays is sorted in lexicographically ascending order."

I'm sorry for being probably too pedantic :)