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#include <iostream>
using namespace std;

const int N = 1e9 + 69;

const int M = (-1) * (1e9 + 69);

int tab[50005];

int tm[50005];
int tmp[50005];

void solve(void) {

    int n; cin >> n;

    for (int i = 1; i <= n; i++) {
        cin >> tab[i];
    }

    int res = 0;

    tm[1] = tab[1];
    tmp[1] = tab[1];

    for (int i = 2; i < n; i += 2) {

        if (tm[i - 1] > tab[i] and tab[i + 1] > tab[i]) tm[i + 1] = tab[i + 1];

        else if (tab[i] >= tm[i - 1]) res++, tm[i + 1] = tab[i + 1];

        else res++, tm[i + 1] = N;

    }

    if (n % 2 == 0 and tm[n - 1] <= tab[n]) res++;

    int w = res;

    res = 0;

    for (int i = 2; i < n; i += 2) {

        if (tmp[i - 1] < tab[i] and tab[i + 1] < tab[i]) tmp[i + 1] = tab[i + 1];

        else if (tab[i] <= tmp[i - 1]) res++, tmp[i + 1] = tab[i + 1];

        else res++, tmp[i + 1] = M;

    }

    if (n % 2 == 0 and tmp[n - 1] >= tab[n]) res++;

    cout << min(res, w);

    return;
}

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

    solve();
}