CF888A Local Extrema

You are given an array $ a $ . Some element of this array $ a_{i} $ is a local minimum iff it is strictly less than both of its neighbours (that is, $ a_{i}a_{i+1} $ ). Since $ a_{1} $ and $ a_{n} $ have only one neighbour each, they are neither local minima nor local maxima. An element is called a local extremum iff it is either local maximum or local minimum. Your task is to calculate the number of local extrema in the given array.

The first line contains one integer $ n $ ( $ 1

Print the number of local extrema in the given array.