#include <bits/stdc++.h>
using namespace std;
int main() {
  int a = -1, n, c = 0, i, x;
  cin >> n;
  for (i = 0; i < n; i++) {
    cin >> x;
    if (c > x) {
      a += c - x;
      c = x;
    }
    a += x - c;
    c = x;
    a += 2;
  }
  cout << a;
}
