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 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<stdio.h>
int MIN(int a,int b){return a<b?a:b;}
int MAX(int a,int b){return a<b?b:a;}
int f(int a,int b,int c){return  a+b+c-MAX(MAX(a,b),c)-MIN(MIN(a,b),c);}
int main(){
  int n,i,c=0,d[100],b[100]={};
  scanf("%d",&n);
  for(i=0;i<n;i++)scanf("%d",&d[i]);
  for(i=1;i<n-1;i++)b[f(d[i-1],d[i],d[i+1])]++;
  for(i=0;i<100;i++){
    if(b[i])c++;
  }
  printf("%d\n",c);
  return 0;
}