Need to sum rows from multiple tables with varying layouts

I have several tables that I need to sum and combine into one master table. The problem is that not all the tables have the same layout of products. How would you combine the varying tables in order to create a master table where the products are summed accurately from the varying input tables?

Here's an example of the layout (below and attached in Excel). Lastly, my apologies if this has been answered already but after looking through the forum for about 20 mins, I couldn't find a similar example.

CATEGORY 1 AMOUNT
Product A 5
Product B 8
Product G 11
Product H 3

CATEGORY 2 AMOUNT
Product B 14
Product C 5
Product E 6
Product H 12

CATEGORY 3 AMOUNT
Product A 20
Product C 14
Product D 3
Product G 5

example table.jpg