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