#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, ans = 0, cur = 0, h;
  cin >> n;
  cin >> cur;
  ans += cur + 1;
  for (int i = 1; i < n; i++) {
    cin >> h;
    ans += (abs(h - cur) + 2);
    cur = h;
  }
  cout << ans;
  return 0;
}
