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