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