#include <bits/stdc++.h>   using namespace std;   int main() {     int n;     cin >> n;     int a[105];     int cnt = 0;     for (int i = 1; i <= n; i++) cin >> a[i];     for (int i = 2; i <= n - 1; i++) {       if (a[i] == 0 && a[i - 1] == a[i + 1] && a[i + 1] == 1) {         a[i + 1] = 0;         cnt++;       }     }     cout << cnt << endl;     return 0;   }   