#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, h, sum = -1, curr = 0;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> h;
    if (h >= curr) {
      sum += h - curr + 1;
      curr = h;
    } else if (curr > h) {
      sum += curr - h + 1;
      curr = h;
    }
  }
  sum += n;
  cout << sum;
  return 0;
}
