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#include <iostream>

using namespace std;

int main() {
    int n;
    cin >> n;
    int a[n];
    for (int i = 0; i < n; ++i) {
        cin >> a[i];
    }
    int changes1 = 0;
    int changes2 = 0;

    for (int i = 0; i < n - 1; ++i) {
        int change = a[i] - a[i + 1];
        if (i%2==1) {
            if (change <= 0) {
                changes1++;
                i++;
            }
        } else if (change >= 0) {
            changes1++;
            i++;
        }
    }

    for (int i = 0; i < n - 1; ++i) {
        int change = a[i] - a[i + 1];
        if (i%2==0) {
            if (change <= 0) {
                changes2++;
                i++;
            }
        } else if (change >= 0) {
            changes2++;
            i++;
        }
    }


    cout << min(changes1,changes2);

    return 0;
}