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//2022-12-12
//author: Marcin Rolbiecki
#include <bits/stdc++.h>
using namespace std;

const int maxN = 5e4+10;

int n, A[maxN], ans = INT_MAX;

int main () {
		
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	
	cin >> n;
	
	for (int i = 0; i < n; i++)
		cin >> A[i];
		
	int res = 0, l = A[0];
	for (int i = 1; i < n; i++) {
		
		if (i % 2 == 0) {
			if (A[i] <= l) res++, l = 1e9;
			else l = A[i];
		}
		else {
			if (A[i] >= l) res++, l = -1e9;
			else l = A[i];
		}
	}
	ans = min(ans, res);
	
	res = 0, l = A[0];
	for (int i = 1; i < n; i++) {
		
		if (i % 2 == 0) {
			if (A[i] >= l) res++, l = -1e9;
			else l = A[i];
		}
		else {
			if (A[i] <= l) res++, l = 1e9;
			else l = A[i];
		}
	}
	
	ans = min(ans, res);
	cout << ans;
	
	return 0;
}