Step-1: General tab
Give the  basic details for your discount rule and choose "Quantity Based" as your discount method.

Step-2: Condition tab
 
In the condition tab, choose
Apply To = Specific products and then select the product for which the discount should be applicable. 

For example, select Laptop.

Step-3: Discount tab

Set the discount range and value like below:
Min-Quantity = 1
Max quantity = 999
Adjustment type = Product discount
Value = Select any two products (that needs to be discounted)

Save.

Step-4: Frontend demo

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