I saw this on AIO 2020 and have no idea.

On an interval ranged 1 ~ L there are N segments (Ai, Bi)

You can add at most k extra segments with length X.

What is the longest continuous interval you can get that is covered by segments?

2 <= L <= 10^9

0 <= k <= 10^9

N <= 10^5

sample

I've just been tring the blog function,and then had 28 bad votes-_-||..I wanna know why..And what's "Contribution"?