It was too late to find another way. During this period, the King of Qi attacked Korea: "Qi attacking Liang Enemy at the Gates běng lín chéng Xià shows that the enemy has reached his own wall, and the antonym of urgent need is as safe as Mount Tai; Can't write "Cheng". Synonym is urgent. Metaphor the situation is very critical. Source "Warring States Policy Qi Ce II"; It can't be pronounced "cénɡ". "It is generally used as a predicate. "Structure subject-predicate form. Pronunciation city, clause; Once ~, sit back and relax, such as calling out early. Strive for initiative. Distinguish the city, safe and sound, Liang. Usage describes the situation is very dangerous and urgent.