CF602B Approximating a Constant Range

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 of $ n $ data points $ a_{1},...,a_{n} $ . There aren't any big jumps between consecutive data points — for each $ 1

The first line of the input contains a single integer $ n $ ( $ 2

Print a single number — the maximum length of an almost constant range of the given sequence.

In the first sample, the longest almost constant range is $ [2,5] $ ; its length (the number of data points in it) is 4. In the second sample, there are three almost constant ranges of length $ 4 $ : $ [1,4] $ , $ [6,9] $ and $ [7,10] $ ; the only almost constant range of the maximum length $ 5 $ is $ [6,10] $ .