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**. Do any of you have an idea for a more clean alternative? 

I have tried shiznit and shoot (which most websites suggested as alternatives), but they don't sound great.