"Every n-product is free" - where to find the right plugin?

Question

WordPress

I'm looking for a free plugin to implement the functionality of the "3 + 1" type (when buying 3 units of the product, the 4th as a gift), but I can’t find a suitable one.

This plugin has similar functionality (7th point): www.flycart.org/woocommerce-discount-rules-examples?utm_source=woo-discount-rules-v2