#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int h[n];
  long long s = 0;
  for (int i = 0; i < n; i++) cin >> h[i];
  s = h[0] + 1;
  for (int i = 1; i < n; i++) {
    if (h[i - 1] > h[i])
      s += h[i - 1] - h[i] + 2;
    else if ((h[i - 1] == h[i]))
      s += 2;
    else
      s += 2 + (h[i] - h[i - 1]);
  }
  cout << s;
}
