#include<stdio.h>
int main(){
	int a[10000],n,i,count=0;
    scanf("%d",&n);
	for(i=0;i<n;i++){
		scanf("%d",&a[i]);
	}
	for(i=1;i<n-1;i++){
		if(a[i]<a[i-1]&&a[i]<a[i+1]){
			count++;
		}
		if(a[i]<a[i-1]&&a[i]==a[i+1]){
			count++;
		}
	}printf("%d",count);
return 0;
}