It has a risk of being used for illicit activities
like validation rules for input. In other ways, they were very primitive,
，更多细节参见搜狗输入法2026
"I listened to the discussion, they knew I was the commander, and I said: 'It sounds like we can do it'."
// 易错点3：处理最终结果为空的场景（比如num="10"，k=2）