#include <bits/stdc++.h>
using namespace std;
long long n, ans, h, cur;
int main() {
  std::ios::sync_with_stdio(false);
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> h;
    ans += abs(h - cur) + 1;
    cur = h;
  }
  cout << ans + n - 1 << endl;
}
