#include <iostream>

using namespace std;

int N;
int sol;
int V[100005];

int main()
{
    cin >> N;
    for (int i = 1; i <= N; ++i)
        cin >> V[i];

    for (int i = 1; i <= N - 2; ++i)
    {
        if (V[i] < V[i + 1] && V[i + 1] > V[i + 2])
        {
            ++sol;
            i += 2;
        }
    }

    cout << sol << '\n';

    return 0;
}