#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  int sn;
  int h, ph;
  int sum;
  cin >> n;
  sn = n;
  if (n != 0) {
    cin >> h;
    cout << endl;
    sum = h;
    ph = h;
    n--;
    while (n != 0) {
      cin >> h;
      if (ph <= h) {
        sum += ((h / ph) - 1) * ph + (h % ph);
      } else {
        sum += ((ph / h) - 1) * h + (ph % h);
      }
      ph = h;
      n--;
    }
    sum = sum + sn + sn - 1;
    cout << sum;
  }
  return 0;
}
