Write a joke related to the given words.
Doctor, police
Okay, here's a joke that relates to both doctors and police: 

Why did the policeman go to the doctor? 
Because he was an undercover cop and he had caught a "flu."
Complete the following task based on the instruction and optional input provided.### Instruction:
Write a joke related to the given words.

### Input:
Doctor, police

### Output:
Okay, here's a joke that relates to both doctors and police: 

Why did the policeman go to the doctor? 
Because he was an undercover cop and he had caught a "flu."