import java.util.*;
import static java.lang.System.*;

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();
		int ans = 0;
		for (int i = 1; i < n - 1; i++) {
			int cnt = 0;
			if ( Math.max(p[i], p[i - 1]) == p[i])
				cnt++;
			if ( Math.max(p[i], p[i + 1]) == p[i])
				cnt++;
			if (cnt == 1)
				ans++;
		}
		out.println(ans);
		
	}
} import java.util.*; util.* java import static java.lang.System.*; import static java.lang.System.*; import static java.lang.System.*; 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();
		int ans = 0;
		for (int i = 1; i < n - 1; i++) {
			int cnt = 0;
			if ( Math.max(p[i], p[i - 1]) == p[i])
				cnt++;
			if ( Math.max(p[i], p[i + 1]) == p[i])
				cnt++;
			if (cnt == 1)
				ans++;
		}
		out.println(ans);
		
	}
} 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();
		int ans = 0;
		for (int i = 1; i < n - 1; i++) {
			int cnt = 0;
			if ( Math.max(p[i], p[i - 1]) == p[i])
				cnt++;
			if ( Math.max(p[i], p[i + 1]) == p[i])
				cnt++;
			if (cnt == 1)
				ans++;
		}
		out.println(ans);
		
	} 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 = 1; i < n - 1; i++) {
			int cnt = 0;
			if ( Math.max(p[i], p[i - 1]) == p[i])
				cnt++;
			if ( Math.max(p[i], p[i + 1]) == p[i])
				cnt++;
			if (cnt == 1)
				ans++;
		}
		out.println(ans);
		
	} 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] p i sc.nextInt() sc.nextInt sc int ans = 0; ans 0 for (int i = 1; i < n - 1; i++) {
			int cnt = 0;
			if ( Math.max(p[i], p[i - 1]) == p[i])
				cnt++;
			if ( Math.max(p[i], p[i + 1]) == p[i])
				cnt++;
			if (cnt == 1)
				ans++;
		} int i = 1; int i = 1; i 1 i < n - 1 i n - 1 n 1 i++ i++ i {
			int cnt = 0;
			if ( Math.max(p[i], p[i - 1]) == p[i])
				cnt++;
			if ( Math.max(p[i], p[i + 1]) == p[i])
				cnt++;
			if (cnt == 1)
				ans++;
		} {
			int cnt = 0;
			if ( Math.max(p[i], p[i - 1]) == p[i])
				cnt++;
			if ( Math.max(p[i], p[i + 1]) == p[i])
				cnt++;
			if (cnt == 1)
				ans++;
		} int cnt = 0; cnt 0 if ( Math.max(p[i], p[i - 1]) == p[i])
				cnt++; Math.max(p[i], p[i - 1]) == p[i] Math.max(p[i], p[i - 1]) Math.max Math p[i] p i p[i - 1] p i - 1 i 1 p[i] p i cnt++ cnt if ( Math.max(p[i], p[i + 1]) == p[i])
				cnt++; Math.max(p[i], p[i + 1]) == p[i] Math.max(p[i], p[i + 1]) Math.max Math p[i] p i p[i + 1] p i + 1 i 1 p[i] p i cnt++ cnt if (cnt == 1)
				ans++; cnt == 1 cnt 1 ans++ ans out.println(ans) out.println out ans String[] args args 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();
		int ans = 0;
		for (int i = 1; i < n - 1; i++) {
			int cnt = 0;
			if ( Math.max(p[i], p[i - 1]) == p[i])
				cnt++;
			if ( Math.max(p[i], p[i + 1]) == p[i])
				cnt++;
			if (cnt == 1)
				ans++;
		}
		out.println(ans);
		
	}
} 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();
		int ans = 0;
		for (int i = 1; i < n - 1; i++) {
			int cnt = 0;
			if ( Math.max(p[i], p[i - 1]) == p[i])
				cnt++;
			if ( Math.max(p[i], p[i + 1]) == p[i])
				cnt++;
			if (cnt == 1)
				ans++;
		}
		out.println(ans);
		
	}
} Main
import java.util.*;
import static java.lang.System.*;

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();
		int ans = 0;
		for (int i = 1; i < n - 1; i++) {
			int cnt = 0;
			if ( Math.max(p[i], p[i - 1]) == p[i])
				cnt++;
			if ( Math.max(p[i], p[i + 1]) == p[i])
				cnt++;
			if (cnt == 1)
				ans++;
		}
		out.println(ans);
		
	}
}