#include <bits/stdc++.h>
using namespace std;
unsigned long long n, h[100000], sum;
int main() {
  cin >> n;
  for (int i = 0; i < n; i++) cin >> h[i];
  for (int i = 0; i < n - 1; i++) {
    if (h[i] < h[i + 1])
      sum += (h[i + 1] - h[i]) + 1;
    else if (h[i] == h[i + 1])
      sum += 1;
    else
      sum += h[i] - h[i + 1] + 1;
  }
  sum += h[0] + n;
  cout << sum << endl;
  return 0;
}
