Red flag is a joke.

There are two old people who have been working together for more than a month and don't know each other's names. On this day, old man A asked old man B what his name was, and old man B said my name was not pleasant to listen to. Guess, an idea, his name is not nice. Could it be that your surname is Qiu, B says Qiu lives next door, A thinks your surname is Egg, B says you live in a hospital with your surname Egg, A thinks your surname is Urine, and B says you live with him.