#include<stdio.h>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <algorithm>
#include <sstream>
#include <iostream>
#include <string>
#include <stdio.h>

using namespace std;

int main() {

	int N,A[105], ans = 0; 
	cin >> N;
	for (int i = 0; i < N; i++) cin >> A[i];

	for (int i = 0; i < N - 2; i++) {
		int v[3], m = 1000, M = -1;
		for (int j = 0; j < 3; j++) {
			v[j] = A[i+j];
			m = min(m, v[j]);
			M = max(M, v[j]);
		}
		/*
		for (int h = 0; h < 3; h++) cout << v[h] << " ";
		cout << endl;
		*/
		if (v[0] != v[1] && v[0] != v[2] && v[2] != v[1] && ( v[1] == m || v[1] ==M )) {
			ans++;
		}
	}

	cout << ans << endl;

	return 0;
}