How do I do the second part of this with adders? Like on Logism how does it look? I get an error about incompatible width when I try to use NOT gates. What am I doing wrong?

Part A: Utilize an Adder IC to demonstrate the addition operation of two 4-bit numbers: a) Assume that the two numbers are unsigned positive numbers b) Assume that the numbers are in 2s complement form. Note that in this case the output is also 4-bit number in 2s complement form, i.e., the carry output will be ignored