#include <bits/stdc++.h>
using namespace std;
int n, cnt = -1, h, hx;
int main() {
  cin >> n;
  while (n--) {
    cin >> h;
    if (hx > h) {
      cnt += hx - h;
      hx = h;
    }
    cnt += h - hx;
    hx = h;
    cnt += 2;
  }
  cout << cnt;
}
