#include <bits/stdc++.h>
using namespace std;
int main() {
  long n, i, j, k, s;
  cin >> n;
  long a[n];
  for (i = 0; i < n; i++) cin >> a[i];
  s = a[0];
  for (i = 0; i < n - 1; i++) {
    s = s + labs(a[i] - a[i + 1]);
  }
  s = s + n + n - 1;
  cout << s << endl;
  return 0;
}
