Comparing two arrays and getting third array with mismatched elements from both of them [solved]

There are some topics here about arrays issues, but none of them was helpful enough to make me figure it out.

So I have array A[1,2,3] and array B[1,4,3]. I want to compare them and receive array C[2,4]

Additional question:
Does variables in repeating task hold values from previous run before being overwritten by the new one? If no, is there a way to make something like that?