50分

#include<iostream>
#include<cstdio>
using namespace std;

int main(){
	int n,a[20000],ans=0;
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>a[i];
	}
	for(int i=2;i<n;i++){
		if(a[i-1]>a[i]&&a[i+1]>a[i])ans++;
	}
	cout<<ans<<endl;
	
	return 0;
}