#include <bits/stdc++.h>
using namespace std;
int main(int argc, char const* argv[]) {
  int treeCount;
  scanf("%d", &treeCount);
  int prev, curr;
  scanf("%d", &prev);
  int answer = prev + 1;
  for (int i = 1; i < treeCount; ++i) {
    scanf("%d", &curr);
    answer += 1 + abs(curr - prev) + 1;
    prev = curr;
  }
  printf("%d\n", answer);
  return 0;
}
