I am writing a poem for school. The verse with the word I need to change is this:

7 hours is too long
In much too short a day
You really don’t care if you get an answer wrong
Because you don’t care a _____ about radioactive decay

The only thing I can think of is the word shit, but that word is too offensive. I have tried looking for inoffensive alternatives at Real Life English's Not so Offensive Alternatives to Bad Words in English, and wordhippo but these alternatives do not sound great, especially in a poem.

I also searched for don't care a ___ on the free dictionary by Farlex's idioms website and "don't care a fig" came up, alongside some other suggestions I tried from the autofill suggestions. Most worked literally, but I am looking for a more clever and poetic word or words that could be used in a way that relates to my poem. I am not just looking for any old answer. I do not want you to simply search for "don't care a…" on google. I want suggestions that fit creatively into my poem.