#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int tree, sec = 0;
  cin >> tree;
  sec = tree;
  int prev = tree;
  for (int i = 0; i < n - 1; i++) {
    cin >> tree;
    if (tree >= prev)
      sec += tree - prev;
    else {
      sec += prev - tree;
    }
    prev = tree;
  }
  sec += 2 * n - 1;
  cout << sec << endl;
}
