#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i, ctr = 0, j;
  int arr[1000];
  cin >> n;
  for (i = 0; i < n; i++) cin >> arr[i];
  for (i = 0; i < n; i++)
    if (arr[i] == 1) break;
  if (i == n) {
    cout << 0;
    return 0;
  }
  for (j = n - 1; j >= 0; j--)
    if (arr[j] == 1) break;
  if (i == j) {
    cout << 1;
    return 0;
  }
  ctr = 1;
  for (int k = i + 1; k <= j; k++) {
    if (arr[k] == 1)
      ctr++;
    else if (arr[k] == 0 && arr[k - 1] == 1 && arr[k + 1] == 1)
      ctr++;
  }
  cout << ctr;
  return 0;
}
