#include <bits/stdc++.h>
using namespace std;
const int N = 123456;
int h[N];
int main() {
  ios_base::sync_with_stdio(false);
  long long ans = 0ll;
  int n, curr_h;
  cin >> n;
  for (int i = 0; i < n; ++i) {
    cin >> h[i];
  }
  ans += h[0] + n - 1 + n;
  curr_h = h[0];
  for (int i = 1; i < n; ++i) {
    ans += abs(curr_h - min(h[i - 1], h[i]));
    ans += h[i] - min(h[i - 1], h[i]);
    curr_h = h[i];
  }
  cout << ans << endl;
  return 0;
}
