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#include <iostream>

using namespace std;
int n, tab[50005], tab1[50005], tab2[50005], wyn1, wyn2;
int main()
{
    int inf = 1e9;
    cin >> n;
    for(int i = 0; i<n; i++)
    {
        cin >> tab[i];
    }
    tab1[0] = tab[0];
    tab2[0] = tab[0];
    for(int i = 1; i<n; i++)
    {
        if(i%2)
        {
            if(tab[i] > tab1[i-1])
            {
                tab1[i] = tab[i];
            }
            else
            {
                tab1[i] = inf;
                wyn1 ++;

            }
        }
        else
        {
            if(tab[i] < tab1[i-1])
            {
                tab1[i] = tab[i];
            }
            else
            {
                tab1[i] = -inf;
                wyn1++;
            }
        }

    }
    for(int i = 1; i<n; i++)
    {
        if(i%2 == 0)
        {
            if(tab[i] > tab2[i-1])
            {
                tab2[i] = tab[i];
            }
            else
            {
                tab2[i] = inf;
                wyn2++;
            }
        }
        else
        {
            if(tab[i] < tab1[i-1])
            {
                tab2[i] = tab[i];
            }
            else
            {
                tab2[i] = -inf;
                wyn2++;
            }
        }

    }
    cout << min(wyn1, wyn2);

    return 0;
}