#include<stdio.h>
#include<stdlib.h>

int main()
{
	int l=0,n;
	int ar[25];
	scanf("%d",&n);
	scanf("%d%d",&ar[0],&ar[1]);
	for(int i=2;i<n;i++)
	{
		scanf("%d",&ar[i]);
		if((ar[i-1]-ar[i])*(ar[i-2]-ar[i-1])>0) l++;
	}
	printf("%d\n",l);
	return 0;
}

### Prompt

Develop a solution in cpp to the problem described below:

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.

Examples

Input

5
1 3 5 4 2


Output

2


Input

9
9 6 3 2 5 8 7 4 1


Output

5

### Response

```cpp
#include<stdio.h>
#include<stdlib.h>

int main()
{
	int l=0,n;
	int ar[25];
	scanf("%d",&n);
	scanf("%d%d",&ar[0],&ar[1]);
	for(int i=2;i<n;i++)
	{
		scanf("%d",&ar[i]);
		if((ar[i-1]-ar[i])*(ar[i-2]-ar[i-1])>0) l++;
	}
	printf("%d\n",l);
	return 0;
}

```