Formula or macro to combine data

I have data in two columns that I am trying to combine, but keep in separate columns.
So I have:
A 1
B 2
C 3

And I need this:
A 1
A 2
A 3
B 1
B 2
B 3
C 1
C 2
C 3

However, I can't use concatenate because I need to keep the results in separate columns. Is there a quick way of doing this?

Thanks.