#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, cnt = 0;
  cin >> n;
  int a[n];
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  cnt += a[0] + 1;
  for (int i = 0; i < n - 1; i++) {
    cnt += abs(a[i] - a[i + 1]) + 2;
  }
  cout << cnt << "\n";
  return 0;
}
