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/*
	Zadanie: Ornitolog 2
	Autor: Tomasz Kwiatkowski
*/

#include <bits/stdc++.h>

#define fi first
#define se second
#define pb push_back

using namespace std;
typedef long long ll;

int solve(vector<int> arr, bool s)
{
	int res = 0;
	for (int i = 1; i < arr.size(); ++i) {
		if (arr[i - 1] >= arr[i] && !s) {
			arr[i] = 1e9;
			++res;
		} else if (arr[i - 1] <= arr[i] && s) {
			arr[i] = -1e9;
			++res;
		}
		s = !s;
	}
	return res;
}

int main()
{
	ios_base::sync_with_stdio(0); cin.tie(0);
	
	int n;
	cin >> n;
	vector<int> arr(n);
	for (auto& a : arr)
		cin >> a;
	cout << min(solve(arr, 0), solve(arr, 1)) << '\n';
	return 0;
}