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#include <bits/stdc++.h>
using namespace std;
const int NMAX = 5e4, inf = 1e9 + 7;
int n, ans1, ans2;
int a[NMAX + 7];
int32_t main() {
    ios_base::sync_with_stdio(0);
    cout.tie(0);
    cin.tie(0);
	cin >> n;
	for (int i = 1; i <= n; i++){
		cin >> a[i];
	}
	for (int i = 1; i < n; i++){
		if ((i & 1) != (a[i] < a[i + 1]) || a[i] == a[i + 1]){
			ans1++;
			i++;
		}
	}
	for (int i = 1; i < n; i++){
		if ((i & 1) != (a[i] > a[i + 1]) || a[i] == a[i + 1]){
			ans2++;
			i++;
		}
	}
	cout << min(ans1, ans2);
    return 0;
}
// DAWID PAWELEC