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