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#include <iostream>

using namespace std;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    int n, a, last_up, last_down, counter_up = 0, counter_down = 0;
    cin >> n;
    cin >> last_up;

    last_down = last_up;

    for (int i = 1; i < n; i++) {
        cin >> a;
        if (i % 2 == 0) {
            if (a > last_up) {
                last_up = a;
            } else {
                last_up = 1000000000;
                counter_up++;
            }
            if (a < last_down) {
                last_down = a;
            } else {
                last_down = -1000000000;
                counter_down++;
            }
        } else {
            if (a < last_up) {
                last_up = a;
            } else {
                last_up = -1000000000;
                counter_up++;
            }
            if (a > last_down) {
                last_down = a;
            } else {
                last_down = 1000000000;
                counter_down++;
            }
        }
    }

    cout << min(counter_down, counter_up) << "\n";
    return 0;
}