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#include <bits/stdc++.h>
using namespace std;

#define A 1000000000

int main() {
    ios_base::sync_with_stdio(0);
    cout.tie(0);
    cin.tie(0);

    int n; cin >> n;
    vector<int> a(n);
    for(auto &&e : a) cin >> e;

    int sol = INT_MAX;
    for(int s = 0; s < 2; ++s) {
        bool korekta = false;
        int r = 0;
        for(int i = 0; i < n-1; ++i) {
            int c = i%2 == s ? 1 : -1;
            int l = korekta ? c * A : a[i];
            korekta = false;
            if(c*l <= c*a[i+1]) {
                korekta = true;
                ++r;
            }
        }
        sol = min(sol, r);
    }
    cout << sol << '\n';
}