Cart rules with categories

[Kalyma]

Hi, I cant reach discounts from several categories.

 

I mean, i have a promo of school bag + pencil case + book. Taking one of each will have a 30% discount.

 

My site has categories for school bag, pencil case, and books with several products in each category. Doesn't matter wich product you'll take from that category, since i have one design per product (i sell printed indumentary) So, how can I make that cart rule?

 

I already tried with the cart rules config and can't reach that goal.

 

Any thoughts?

 

Thanks!

 

PS: Hope you can undertand my ugly english. I'm from argentina.

 

PSS: My prestashop is 1.6.11