Problem:
Score : 200 points

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.

Sample Input 1

5
1 3 5 4 2

Sample Output 1

2

p_2 = 3 is the second smallest number among p_1 = 1, p_2 = 3, and 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.

Sample Input 2

9
9 6 3 2 5 8 7 4 1

Sample Output 2

5

Solution in C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

/*
ID: Nipun Paul
LANG: C++
PROB: God knows
*/

#include<bits/stdc++.h>
using namespace std;

int main()
{
    int a,b[25],c[3]={0},sum=0,l=0;
    cin>>a;
    for(int i=0; i<a; i++)
    {
        cin>>b[i];
    }
    for(int i=0; i<a-1; i++)
    {
        for(int j=i; j<i+3; j++)
        {
            c[l]=b[j];
            l++;
        }
        sort(c,c+l);
        if(c[1]==b[i+1])
        {
            sum++;
        }
        l=0;
        c[3]={0};
    }
    cout<<sum<<endl;
    return 0;
}