people aged 70 to 79 who have not yet been vaccinated
// drop-oldest: Discard old data to make room
，这一点在heLLoword翻译官方下载中也有详细论述
The price cap is revised by the energy regulator for Great Britain every three months. It said that from April the cost of the average annual dual-fuel bill would drop to £1,641, down from £1,758 today.，更多细节参见safew官方下载
Pakistan bombs Kabul in 'open war' on Afghanistan's Taliban government
// 计算天数：栈非空→栈顶索引-当前索引；栈空→0（易错点3：索引差别写反）