#include <bits/stdc++.h>
using namespace std;
long long n, h, lh = 0, ans = -1;
int main() {
  cin >> n;
  for (long long i = 1; i <= n; i++) {
    cin >> h;
    ans = ans + abs(h - lh) + 2;
    lh = h;
  }
  cout << ans << endl;
  return 0;
}
