#include <bits/stdc++.h>
using namespace std;
int main() {
  long int n;
  scanf("%d", &n);
  long int ans = 0;
  int prev;
  scanf("%d", &prev);
  ans += prev + 1;
  for (long int i = 1; i < n; i++) {
    int h;
    scanf("%d", &h);
    ans += abs(h - prev) + 2;
    prev = h;
  }
  printf("%d", ans);
}
