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#include <bits/stdc++.h>
using namespace std;
constexpr int inf = 1e9;

int rosnie(vector<int> v, int n) {
	int last = inf + 1, licznik = 0;
	for (int i = 0; i < n; i++) {
		if (i % 2 == 0) {
			if (last <= v[i]) {
				v[i] = -inf;
				licznik++;
			}
		} else {
			if (last >= v[i]) {
				v[i] = inf;
				licznik++;
			}
		}

		last = v[i];
	}

	return licznik;
}

int maleje(vector<int> v, int n) {
	int last = -(inf + 1), licznik = 0;
	for (int i = 0; i < n; i++) {
		if (i % 2 == 0) {
			if (last >= v[i]) {
				v[i] = inf;
				licznik++;
			}
		} else {
			if (last <= v[i]) {
				v[i] = -inf;
				licznik++;
			}
		}
		
		last = v[i];
	}

	return licznik;
}

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);

	int n;
	cin >> n;
	vector<int>sequence(n);
	for (auto& x : sequence) cin >> x;

	cout << min(rosnie(sequence, n), maleje(sequence, n)) << '\n';

	return 0;
}