#include <bits/stdc++.h>
typedef long long int lli;
using namespace std;

const int INF = 1e9 + 3;

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
	
	int n;
	cin >> n;
	vector <int> a(n);
	for (int i = 0; i < n; i++){
		cin >> a[i];
	}
	
	int ans = INF, prev, here;
	for (int rep = 0; rep <= 1; rep++){
		prev = a[0], here = 0;
		for (int i = 1; i < n; i++){
			if (i % 2 == rep){
				if (prev <= a[i]){
					here++;
					prev = -INF;
				}
				else{
					prev = a[i];
				}
			}
			else{
				if (prev >= a[i]){
					here++;
					prev = INF;
				}
				else{
					prev = a[i];
				}
			}
		}
		ans = min(ans, here);
	}
	cout << ans << "\n";
	
    return 0;
}