
import java.util.Scanner;
public class Main {
	public static void main(String[] args) throws Exception {
		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();
		}
		int ans = 0;
		for(int i = 2; i < n; i++) {
			int max = p[i-2];
			int min = p[i-2];
			max = Math.max(max, p[i-1]);
			max = Math.max(max, p[i]);
			min = Math.min(min, p[i-1]);
			min = Math.min(min, p[i]);
			if(max != p[i-1] && min != p[i-1]) {
				ans ++;
			}
		}
		System.out.println(ans);
		sc.close();
	}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) throws Exception {
		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();
		}
		int ans = 0;
		for(int i = 2; i < n; i++) {
			int max = p[i-2];
			int min = p[i-2];
			max = Math.max(max, p[i-1]);
			max = Math.max(max, p[i]);
			min = Math.min(min, p[i-1]);
			min = Math.min(min, p[i]);
			if(max != p[i-1] && min != p[i-1]) {
				ans ++;
			}
		}
		System.out.println(ans);
		sc.close();
	}
} Main public static void main(String[] args) throws Exception {
		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();
		}
		int ans = 0;
		for(int i = 2; i < n; i++) {
			int max = p[i-2];
			int min = p[i-2];
			max = Math.max(max, p[i-1]);
			max = Math.max(max, p[i]);
			min = Math.min(min, p[i-1]);
			min = Math.min(min, p[i]);
			if(max != p[i-1] && min != p[i-1]) {
				ans ++;
			}
		}
		System.out.println(ans);
		sc.close();
	} main {
		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();
		}
		int ans = 0;
		for(int i = 2; i < n; i++) {
			int max = p[i-2];
			int min = p[i-2];
			max = Math.max(max, p[i-1]);
			max = Math.max(max, p[i]);
			min = Math.min(min, p[i-1]);
			min = Math.min(min, p[i]);
			if(max != p[i-1] && min != p[i-1]) {
				ans ++;
			}
		}
		System.out.println(ans);
		sc.close();
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int[] p = new int[n]; p new int[n] n for(int i = 0; i < n; i++) {
			p[i] = sc.nextInt();
		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
			p[i] = sc.nextInt();
		} {
			p[i] = sc.nextInt();
		} p[i] = sc.nextInt() p[i] p i sc.nextInt() sc.nextInt sc int ans = 0; ans 0 for(int i = 2; i < n; i++) {
			int max = p[i-2];
			int min = p[i-2];
			max = Math.max(max, p[i-1]);
			max = Math.max(max, p[i]);
			min = Math.min(min, p[i-1]);
			min = Math.min(min, p[i]);
			if(max != p[i-1] && min != p[i-1]) {
				ans ++;
			}
		} int i = 2; int i = 2; i 2 i < n i n i++ i++ i {
			int max = p[i-2];
			int min = p[i-2];
			max = Math.max(max, p[i-1]);
			max = Math.max(max, p[i]);
			min = Math.min(min, p[i-1]);
			min = Math.min(min, p[i]);
			if(max != p[i-1] && min != p[i-1]) {
				ans ++;
			}
		} {
			int max = p[i-2];
			int min = p[i-2];
			max = Math.max(max, p[i-1]);
			max = Math.max(max, p[i]);
			min = Math.min(min, p[i-1]);
			min = Math.min(min, p[i]);
			if(max != p[i-1] && min != p[i-1]) {
				ans ++;
			}
		} int max = p[i-2]; max p[i-2] p i-2 i 2 int min = p[i-2]; min p[i-2] p i-2 i 2 max = Math.max(max, p[i-1]) max Math.max(max, p[i-1]) Math.max Math max p[i-1] p i-1 i 1 max = Math.max(max, p[i]) max Math.max(max, p[i]) Math.max Math max p[i] p i min = Math.min(min, p[i-1]) min Math.min(min, p[i-1]) Math.min Math min p[i-1] p i-1 i 1 min = Math.min(min, p[i]) min Math.min(min, p[i]) Math.min Math min p[i] p i if(max != p[i-1] && min != p[i-1]) {
				ans ++;
			} max != p[i-1] && min != p[i-1] max != p[i-1] max p[i-1] p i-1 i 1 min != p[i-1] min p[i-1] p i-1 i 1 {
				ans ++;
			} ans ++ ans System.out.println(ans) System.out.println System.out System System.out ans sc.close() sc.close sc String[] args args public class Main {
	public static void main(String[] args) throws Exception {
		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();
		}
		int ans = 0;
		for(int i = 2; i < n; i++) {
			int max = p[i-2];
			int min = p[i-2];
			max = Math.max(max, p[i-1]);
			max = Math.max(max, p[i]);
			min = Math.min(min, p[i-1]);
			min = Math.min(min, p[i]);
			if(max != p[i-1] && min != p[i-1]) {
				ans ++;
			}
		}
		System.out.println(ans);
		sc.close();
	}
} public class Main {
	public static void main(String[] args) throws Exception {
		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();
		}
		int ans = 0;
		for(int i = 2; i < n; i++) {
			int max = p[i-2];
			int min = p[i-2];
			max = Math.max(max, p[i-1]);
			max = Math.max(max, p[i]);
			min = Math.min(min, p[i-1]);
			min = Math.min(min, p[i]);
			if(max != p[i-1] && min != p[i-1]) {
				ans ++;
			}
		}
		System.out.println(ans);
		sc.close();
	}
} Main

import java.util.Scanner;
public class Main {
	public static void main(String[] args) throws Exception {
		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();
		}
		int ans = 0;
		for(int i = 2; i < n; i++) {
			int max = p[i-2];
			int min = p[i-2];
			max = Math.max(max, p[i-1]);
			max = Math.max(max, p[i]);
			min = Math.min(min, p[i-1]);
			min = Math.min(min, p[i]);
			if(max != p[i-1] && min != p[i-1]) {
				ans ++;
			}
		}
		System.out.println(ans);
		sc.close();
	}
}
