Shopify script to remove button when you have 2 ATC

[Jef_Poisson]

Hello everyone ! I recently added a button in my cart that says "choose my free gift", so that once the customers have added one product to the cart, they can go get their free item (it's a BOGO on the whole store). However I would like this button to disappear once they have added 2 items to the cart (and to reappear if they only have one ATC) 

Let me know if you can help me.

Thank you