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