CF788A Functions again

Something happened in Uzhlyandia again... There are riots on the streets... Famous Uzhlyandian superheroes Shean the Sheep and Stas the Giraffe were called in order to save the situation. Upon the arriving, they found that citizens are worried about maximum values of the Main Uzhlyandian Function $ f $ , which is defined as follows: In the above formula, $ 1

The first line contains single integer $ n $ ( $ 2

Print the only integer — the maximum value of $ f $ .

In the first sample case, the optimal value of $ f $ is reached on intervals $ [1,2] $ and $ [2,5] $ . In the second case maximal value of $ f $ is reachable only on the whole array.