#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, sum = 0, ck = 0;
  cin >> n;
  int a[n];
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  for (int i = 0; i < n; i++) {
    if (a[i] == 1) {
      if (ck == 0) {
        sum++;
      } else {
        sum += 2;
        ck = 0;
      }
    }
    if (a[i] == 0 && i != 0 && i != n) {
      if (a[i - 1] == 1 && a[i + 1] == 1) {
        sum++;
      } else if (a[i - 1] == 1 && a[i + 1] == 0) {
        ck = 1;
      }
    }
  }
  cout << sum;
}
