#include <bits/stdc++.h>
using namespace std;
int n, a[1010], ans = 0;
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; i++) {
    scanf("%d", &a[i]);
  }
  for (int i = 1; i <= n; i++) {
    if (a[i] == 1) {
      ans++;
      continue;
    }
    if ((a[i] == 0) && (a[i - 1] == 1) && (a[i + 1] == 1)) {
      ans++;
      continue;
    }
  }
  printf("%d", ans);
  return 0;
}
