#include <bits/stdc++.h>
using namespace std;
int main() {
  std::ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  int a[n];
  for (int i = 0; i < n; i++) cin >> a[i];
  int c = 0;
  for (int i = 0; i < n; i++) {
    if (a[i] == 1) c++;
  }
  for (int i = 0; i < n - 2; i++) {
    if (a[i] == 1 && a[i + 1] == 0 && a[i + 2] == 1) c++;
  }
  cout << c << "\n";
  return 0;
}
