#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<int> arr(n);
  for (int i = 0; i < n; i++) {
    cin >> arr[i];
  }
  int tim = 0;
  int height = 0;
  for (int i = 0; i < n - 1; i++) {
    tim += arr[i] - height;
    height = arr[i];
    tim++;
    tim += max(height - arr[i + 1], 0);
    height = min(arr[i + 1], height);
    tim++;
  }
  tim += arr[n - 1] - height;
  tim++;
  cout << tim;
}
