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

typedef long long int ll;

ll llMAX(ll a, ll b){return a>b?a:b;}
ll llMIN(ll a, ll b){return a>b?b:a;}
int MAX(int a, int b){return a>b?a:b;}
int MIN(int a, int b){return a>b?b:a;}
int compare(const void* a, const void* b){return *(int*)a - *(int*)b;}
ll digits(ll a){ll tmp=a; ll cnt=0; while(tmp>0){tmp/=10; cnt+=1;} return cnt;}

int main(void){
    int n;
    scanf("%d", &n);
    int a[n];
    for(int i=0; i<n; i++){
        scanf("%d", &a[i]);
    }

    int res = 0;
    for(int i=0; i<=n-3; i++){
        int max = 0;
        int min = 101;

        for(int j=i; j<i+3; j++){
            max = MAX(max, a[j]);
            min = MIN(min, a[j]);
        }
        if(max==a[i+1] || min==a[i+1]){
            if(a[i]!=a[i+1] && a[i+1]!=a[i+2] && a[i+2]!=a[i]){
                res += 1;
            }
        }
    }

    printf("%d\n", res);
    return 0;
}