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