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#include<bits/stdc++.h>

using namespace std;

int solve(const vector<int>& v, bool up)
{
    int res = 0;
    int count = 0;
    for (int i = 0; i < (int)v.size()-1; i++, up = !up)
    {
        if ((v[i] < v[i+1] && up) || (v[i] > v[i+1] && !up))
        {
            if (count > 0)
            {
                res += (count+1)/2;
                count = 0;
            }
        }
        else
            count++;
    }

    if (count > 0)
    {
        res += (count+1)/2;
        count = 0;
    }

    return res;
}

int main()
{
    ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    int n; cin >> n;
    vector<int> v(n);
    for (auto& e : v)
        cin >> e;

    cout << min(solve(v, true), solve(v, false)) << "\n";
}