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