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