#include<bits/stdc++.h>
using namespace std;
int main() 
{
    long long N;
    cin >> N;
    vector<int> phi(N + 1);
    for (int i = 0; i <= N; i++) 
	{
        cin >> phi[i];
    }
    int cnt = 0;
    for (int i = 0; i < N; i++) 
	{
        if (phi[i] * phi[i + 1] < 0) 
		{
            cnt++;
        }
    }
    cout << cnt << endl;
    return 0;
}

biu biu*2