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#include <bits/stdc++.h>


using namespace std;


int solve(int n, vector <int> &a) {
    int ans = n;

    for (int start = 0; start <= 1; start++) {
        int ansHere = 0, run = 0;
        for (int i = 0; i < n; i++) {
            bool bit;
            if (i < n - 1) {
                if (a[i] == a[i + 1]) {
                    bit = true;
                } else {
                    bit = (i % 2) ^ start ^ (a[i] > a[i + 1]);
                }
            } else {
                bit = false;
            }

            if (bit) {
                run++;
            } else {
                ansHere += (run + 1) / 2;
                run = 0;
            }
        }

        ans = min(ans, ansHere);
    }

    return ans;
}

int main() {
    ios_base::sync_with_stdio(false);

    int n;
    cin >> n;

    vector <int> a(n);
    for (int &ai : a) {
        cin >> ai;
    }

    cout << solve(n, a);

    return 0;
}