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// orn2.cpp : This file contains the 'main' function. Program execution begins and ends there.
//

#define _CRT_SECURE_NO_WARNINGS

#include <cstdio>
#include <algorithm>

int requiredChanges(int n, int* sounds, bool up)
{
	int changes = 0;
	for (int i = 0; i < n - 1; i++)
	{
		if (up && sounds[i] >= sounds[i + 1])
		{
			changes++;
			i++;
			continue;
		}
		if (!up && sounds[i] <= sounds[i + 1])
		{
			changes++;
			i++;
			continue;
		}
		up = !up;
	}

	return changes;
}

int main()
{
	int n;
	scanf("%d", &n);
	int* sounds = new int[n];
	for (int i = 0; i < n; i++)
	{
		scanf("%d", sounds + i);
	}

	int minChanges = 1e9;

	minChanges = std::min(minChanges, requiredChanges(n, sounds, true));
	minChanges = std::min(minChanges, requiredChanges(n, sounds, false));

	printf("%d", minChanges);
	return 0;
}