import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] P = new int[N];
        for (int i = 0; i < N; i++) {
            P[i] = sc.nextInt();
        }
        sc.close();

        System.out.println(OrdinaryNumber(N, P, 1));
    }
    public static int OrdinaryNumber(int N, int[] P, int index) {
        if (N - 1 <= index) {
            return 0;
        }
        if ((P[index - 1] < P[index] && P[index] < P[index + 1]) ||
            (P[index + 1] < P[index] && P[index] < P[index - 1])) {
            return 1 + OrdinaryNumber(N, P, index + 1);
        }
        return OrdinaryNumber(N, P, index + 1);
    }
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz