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