#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int h[100001], n, i, s = 0;
  cin >> n;
  for (i = 0; i < n; i++) cin >> h[i];
  s = s + n + h[0];
  for (i = 0; i < n - 1; i++) {
    if (h[i] > h[i + 1]) {
      s = s + h[i] - h[i + 1];
      h[i] = h[i + 1];
    }
    if (h[i] < h[i + 1]) s = s + h[i + 1] - h[i];
    s++;
  }
  cout << s;
  return 0;
}
