#include <bits/stdc++.h>
using namespace std;
int n, m;
int h[100005];
int main() {
  scanf("%d", &n);
  for (int i = 0; i < n; i++) {
    scanf("%d", &h[i]);
  }
  int ans = 0;
  int last = 0;
  for (int i = 0; i < n - 1; i++) {
    ans += h[i] - last + 1;
    if (h[i] <= h[i + 1]) {
      last = h[i];
      ans++;
    } else {
      ans += h[i] - h[i + 1] + 1;
      last = h[i + 1];
    }
  }
  ans += h[n - 1] - last + 1;
  printf("%d\n", ans);
}
