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 $p_{i + 1}$.

Input is given from Standard Input in the following format:

```
$n$
$p_1$ $p_2$ $...$ $p_n$
```

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

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

2

$p_2=3$ is the second smallest number among $p_1=1, p_2=3, p_3=5$. Also, $p_4=4$ is the second smallest number among $p_3=5, p_4=4$, and $p_5=2$. These two elements satisfy the condition.