When Xellos was doing a practice course in university, he once had to measure the intensity of an effect that slowly approached equilibrium. A good way to determine the equilibrium intensity would be choosing a sufficiently large number of consecutive data points that seems as constant as possible and taking their average. Of course, with the usual sizes of data, it's nothing challenging — but why not make a similar programming contest problem while we're at it?

You're given a sequence ofndata pointsa₁, ..., a_n. There aren't any big jumps between consecutive data points — for each1 ≤ i < n, it's guaranteed that|a_i + 1 - a_i| ≤ 1.

A range[l, r]of data points is said to bealmost constantif the difference between the largest and the smallest value in that range is at most1

Find the length of the longest almost constant range.