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#include <iostream>
#include <cmath>

using namespace std;

int distanceToAlternating(int *data, int n, int start)
{
    int distance = 0;
    int hasToBe = -start;
    for (int i = 1; i < n; ++i)
    {
        if (hasToBe == 1)
        { // has to be greater
            if (data[i] <= data[i - 1])
            {
                ++distance;
                ++i;
            }
            else
            {
                hasToBe = -hasToBe;
            }
        }
        else
        { // has to be less
            if (data[i] >= data[i - 1])
            {
                ++distance;
                ++i;
            }
            else
            {
                hasToBe = -hasToBe;
            }
        }
    }
    return distance;
}

int main()
{
    int n;
    cin >> n;
    int *data = new int[n];

    for (int i = 0; i < n; ++i)
    {
        cin >> data[i];
    }

    int distanceLow = distanceToAlternating(data, n, -1);
    int distanceHigh = distanceToAlternating(data, n, 1);

    cout << min(distanceLow, distanceHigh) << endl;

    delete[] data;
    return 0;
}