#include <iostream>
#include <fstream>
#include <algorithm>
#include <math.h>
#include <string>
#include <vector>
#include <stdio.h>
#include <queue>
#include <set>

#define LL long long
#define pb push_back
#define lm 100001
#define MOD 1000000007

using namespace std;
int n,x,res=0;
vector<int> l;
int main(){

    //freopen("data.txt","r",stdin);
    scanf("%d",&n);
    for(int i=0; i<n; i++)
    {
        scanf("%d",&x);
        l.pb(x);
    }
    for(int i=1; i<n-1; i++)
    {
        if(l[i-1]<l[i] && l[i]>l[i+1])
            {
                res++;
            }
    }
    cout<<res;
    return 0;
}