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#include <iostream>
#include <vector>

using namespace std;

int main()
{
    int n;
    cin >> n;
    vector<int> tab(n);
    for (int i = 0; i < n; i++)
        cin >> tab[i];

    int last = tab[0];
    int w1 = 0;
    bool r = false;
    for (int i = 1; i < n; i++)
    {
        if (r && tab[i] <= last)
        {
            w1++;
            last = 1e9;
        }
        else if (!r && tab[i] >= last)
        {
            w1++;
            last = -1e9;
        }
        else
        {
            last = tab[i];
        }
        r = !r;
    }
    r = true;
    int w2 = 0;
    last = tab[0];
    for (int i = 1; i < n; i++)
    {
        if (r && tab[i] <= last)
        {
            w2++;
            last = 1e9;
        }
        else if (!r && tab[i] >= last)
        {
            w2++;
            last = -1e9;
        }
        else
        {
            last = tab[i];
        }
        r = !r;
    }
    cout << min(w1, w2) << endl;
    return 0;
}