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