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#include <bits/stdc++.h>

using namespace std;



int MAX = 1000000000;
int MIN = -1000000000;

int main() {
    int size;
    cin >> size;
    int sounds[50001];
    int sounds2[50001];
    for (int i = 0; i < size; i++) {
        cin >> sounds[i];
        sounds2[i] = sounds[i];
    }
    bool change = false;
    int changes1 = 0;
    int changes2 = 0;
    for (int i = 1; i < size; i++) {
        if (sounds[i] < sounds[i - 1] && !change) {
            sounds[i] = MAX;
            changes1++;
        } else if (sounds[i] > sounds[i - 1] && change) {
            sounds[i] = MIN;
            changes1++;
        } else if (sounds[i] == sounds[i - 1]) {
            if (!change) {
                sounds[i] = MAX;
            } else {
                sounds[i] = MIN;
            }
            changes1++;
        }
        if (sounds2[i] > sounds2[i - 1] && !change) {
            sounds2[i] = MIN;
            changes2++;
        } else if (sounds2[i] < sounds2[i - 1] && change) {
            sounds2[i] = MAX;
            changes2++;
        } else if (sounds2[i] == sounds2[i - 1]) {
            if (!change) {
                sounds2[i] = MIN;
            } else {
                sounds2[i] = MAX;
            }
            changes2++;
        }
        change = !change;
    }

    cout << min(changes1, changes2) << endl;
    return 0;
}