#include <bits/stdc++.h>
using namespace std;
int Trees[123456], N, ANS = 0;
int main() {
  scanf("%d", &N);
  for (int i = 0; i < N; i++) {
    int h;
    scanf("%d", &h);
    Trees[i] = h;
  }
  int intialH = 0;
  for (int i = 0; i < N; i++) {
    ANS += Trees[i] - intialH + 1;
    intialH = Trees[i];
    if (i == N - 1) break;
    if (Trees[i + 1] >= intialH) {
      ANS++;
      intialH = Trees[i];
    } else {
      ANS += Trees[i] - Trees[i + 1] + 1;
      intialH = Trees[i + 1];
    }
  }
  cout << ANS << endl;
  return 0;
}
