Magento 2: buy X items Get Y cheapest items from X free

Question

I am using extension Amasty Special Promotions https://amasty.com/special-promotions-for-magento-2.html .

I need one promotion Like this

Rule Name: Buy 15 get 5 free Details: If I buy the 15 items then from those 15 the 5 cheapest should be free. And next it should apply on the qty 30 and then 45 and so on.

Current Rule Configurations:

Conditions:

If cart total quantity >= 15 & category is 342

Actions:

Apply: The Cheapest, also for Buy 1 get 1 free
Discount Amount: 100
Discount Qty Step (Buy X): 3

In the current implementation, I get 5 cheapest free items when total quantity is 15 but after that on 18 get one more free and 21 one more free and so on

Question: Is there any way in the current module to get the discount on 15, 30, 45 ... and on each step get 5 cheapest?

Note: I am working on it and my purpose to share here if someone had the same solution then we can share else after I implement I will share here.

Here is the example

Promotion rules

1. If the customer will buy the X items then he will get Y cheapest items free
2. The rule should be calculated on buy X,2X,3X,...

Run time Example

Rule: Buy 15 get 5 free

Cart:

Stage 1:

Item A

    qty: 4

    Price per item: 5



Item B

    qty: 10

    price per item: 10



Discount: 0



Stage 2:

Item A

    qty: 4

    Price per item: 5

Item B

    qty : 11

    price per item: 10

Discount: 25



Stage 3:

Item A

    qty:  7

    Price per item: 5

Item B

    qty : 11

    price per item: 10

Discount: 25



Stage 4:

Item A

    qty:  19

    Price per item: 5

Item B

    qty : 11

    price per item: 10

Discount: 50

Thank You!

Answer 1

As mentioned in the Documentation, In Discount Qty Step you need to specify a step by which a discount will be iterated.

So in your it will be:

Discount Qty Step (Buy X): 15