Subtractor

One of the ways to implement a subtractor is to rearrange the equation this way.

F = A B

F = A + (-B)

We need the adder block to add 2 numbers (2s complement)

What extra block do you need?

How would you connect this block to the adder block?

How do you implement the function inside the parenthesis?

What does the logic diagram look like?

Please use a 4-bit number as an example.