Show first the products on sale and at the end the products out of stock.

[nevuz]

Hello.

Sorry for my bad English.

I would like that in the product page of my Prestashop appear at the end the out of stock products and at the beginning the products that are on sale. The out of stock products already appear at the end because I already changed the pagination option of 'Product configuration' putting 'Sort products by: Product Quantity' and in descending order... but to put first the ones that are on sale I don't know.

Thanks in advance.