#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, h, h0(0);
  cin >> n;
  int t = n + n - 1;
  while (n--) {
    cin >> h;
    t += abs(h - h0);
    h0 = h;
  }
  cout << t << endl;
  return 0;
}
