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#include <bits/stdc++.h>
using namespace std;
int tab[1000006];
int sec[1000006];
int MAX = 1000000000;
int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int n;
    cin >> n;
    for (int i = 1; i <= n; i++)
        cin >> tab[i];
    int ans1 = 0, ans2 = 0, ans = n;
    sec[1] = tab[1];
    for (int i = 2; i <= n; i++) {
        if (i%2 == 1) {
            if (tab[i] > sec[i-1]) {
                sec[i] = tab[i];
            }
            else {
                ans1++;
                sec[i] = MAX;
            }
        }
        else {
            if (tab[i] < sec[i-1]) {
                sec[i] = tab[i];
            } else {
                ans1++;
                sec[i] = -MAX;
            }
        }
    }
    ans = min(ans1, ans);
    ans1 = 0;
    for (int i = 1; i <= n; i++)
        sec[i] = 0;
    sec[1] = tab[1];
    for (int i = 2; i <= n; i++) {
        if (i%2 == 0) {
            if (tab[i] > sec[i-1]) {
                sec[i] = tab[i];
            }
            else {
                ans1++;
                sec[i] = MAX;
            }
        }
        else {
            if (tab[i] < sec[i-1]) {
                sec[i] = tab[i];
            } else {
                ans1++;
                sec[i] = -MAX;
            }
        }
    }
    ans = min(ans, ans1);
    cout << ans;
    return 0;
}