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#include <iostream>
using namespace std;
const int N = 50 * 1000 + 3;
const int LIM = 1e6; int n;
int tab[N];
int now[N];
int sprawdz()
{
	int zmiany = 0;
	now[1] = tab[1];
	if (tab[1] == LIM)
	{
		now[1] = -LIM;
		zmiany = 1;
	}
	for (int i = 2; i <= n; i++)
	{
		if (i % 2 == 0)
		{
			now[i] = tab[i];
			if (tab[i] <= now[i - 1])
			{
				now[i] = LIM;
				zmiany++;
			}
		}
		else
		{
			now[i] = tab[i];
			if (tab[i] >= now[i - 1])
			{
				now[i] = -LIM;
				zmiany++;
			}
		}
	}
	return zmiany;
}
int main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cin >> n;
	for (int i = 1; i <= n; i++) cin >> tab[i];
	int jed = sprawdz();
	for (int i = 1; i <= n; i++) tab[i] = -tab[i];
	int dwa = sprawdz();
	cout << min(jed, dwa);
}