Come up with a funny knock-knock joke.
Knock, knock.

Who’s there?

Boo.

Boo who?

Aw, don’t cry! It’s just a knock-knock joke.
Complete the following task based on the instruction and optional input provided.### Instruction:
Come up with a funny knock-knock joke.

### Output:
Knock, knock.

Who’s there?

Boo.

Boo who?

Aw, don’t cry! It’s just a knock-knock joke.