the first append allocates a backing store of length 4 from the stack.
"On top of this, Reddit's community moderators set and enforce subreddit-specific rules that can be even stricter."
，这一点在51吃瓜中也有详细论述
One 2025 estimate is that food crime costs the global economy around £81bn ($110bn) a year.
if (n <= 1) return;