#include <bits/stdc++.h>
using namespace std;
int main() {
  int x, y, res = 0, temp = 0;
  cin >> x;
  for (int i = 0; i < x; i++) {
    cin >> y;
    res += abs(temp - y);
    res += 2;
    temp = y;
  }
  cout << --res << endl;
}
