Two columns of 4-digit numbers and return uni

Hello, I need a macro to compare two columns of numbers. And I am totally new at macros. I'll need some detailed instructions please.

I must eliminate the numbers that appear in both columns. These numbers may be listed in different rows though.
And it should leave me with the numbers that occurred only once.

data I should be left with only a right-hand column
42 42 41
40 41 37
39 40 35
38 39
36 38
37
36
35 thanks for any help. K