#include <iostream>

using namespace std;

enum class Direction { HEIGHER, LOWER };

int changes(int record[], int n, Direction direction) {

	int result = 0, i = 1;
	while (i < n) {
		if (direction == Direction::HEIGHER) {
			if (record[i] <= record[i-1]) {
				result++;
				i += 2;
			}
			else {
				direction = Direction::LOWER;
				i++;
			}
		}
		else {
			if (record[i] >= record[i-1]) {
				result++;
				i += 2;
			}
			else {
				direction = Direction::HEIGHER;
				i++;
			}
		}
	}
	return result;
}

int main() {

	ios_base::sync_with_stdio(false);
	cin.tie(NULL);

	int n;
	cin >> n;
	int record[n];

	for (int i = 0; i < n; i++)
		cin >> record[i];

	int changes1 = changes(record, n, Direction::HEIGHER);
	int changes2 = changes(record, n, Direction::LOWER);

	cout << (changes1 < changes2 ? changes1 : changes2) << "\n";

	return 0;
}