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