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