Problem:
Score : 200 points

Problem Statement

We have a permutation p = {p_1,\ p_2,\ ...,\ p_n} of {1,\ 2,\ ...,\ n}.

Print the number of elements p_i (1 < i < n) that satisfy the following condition:

p_i is the second smallest number among the three numbers p_{i - 1}, p_i, and p_{i + 1}.

Constraints

All values in input are integers.

3 \leq n \leq 20

p is a permutation of {1,\ 2,\ ...,\ n}.

Input

Input is given from Standard Input in the following format:

n
p_1 p_2 ... p_n

Output

Print the number of elements p_i (1 < i < n) that satisfy the condition.

Sample Input 1

5
1 3 5 4 2

Sample Output 1

2

p_2 = 3 is the second smallest number among p_1 = 1, p_2 = 3, and p_3 = 5. Also, p_4 = 4 is the second smallest number among p_3 = 5, p_4 = 4, and p_5 = 2. These two elements satisfy the condition.

Sample Input 2

9
9 6 3 2 5 8 7 4 1

Sample Output 2

5

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.Arrays;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

		int array[] = null;
		int count = 0;

		Scanner scanner = new Scanner(System.in);

		//入力値を扱いやすいように配列化
		for(int i = 0; scanner.hasNext(); i++) {
			if(i == 0) array = new int[Integer.parseInt(scanner.next())];

			array[i] = Integer.parseInt(scanner.next());
		}

		for(int i = 0; i < (array.length -2); i++) {
			int temp[] = new int[] {array[i], array[i+1], array[i+2]};
			Arrays.sort(temp);
			if(array[i+1] == temp[1]) count++;
		}

		System.out.print(count);

		scanner.close();
	}
}