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