#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int i, j, k;
  long long int n, count = -1;
  cin >> n;
  long long int a[n];
  for (i = 0; i < n; i++) cin >> a[i];
  long long int c = 0;
  for (i = 0; i < n; i++) {
    count++;
    count += (a[i] - c);
    count++;
    if (a[i + 1] < a[i]) {
      count += (a[i] - a[i + 1]);
      c = a[i + 1];
    } else
      c = a[i];
  }
  cout << count;
  return 0;
}
