Problem Statement

We have a permutation $p$ = {$p_1,\ p_2,\ ...,\ p_n$} of {$1,\ 2,\ ...,\ n$}.

Print the number of elements $p_i$ ($1 < i < n$) that satisfy the following condition:

• $p_i$ is the second smallest number among the three numbers $p_{i - 1}$, $p_i$, and $p_{i + 1}$.

Constraints

• All values in input are integers.
• $3 \leq n \leq 20$
• $p$ is a permutation of {$1,\ 2,\ ...,\ n$}.

Input

Input is given from Standard Input in the following format:

n
p_1 p_2 ... p_n

Output

Print the number of elements $p_i$ ($1 < i < n$) that satisfy the condition.