One Column Into Two Using Alternate Rows?

I have a single column of data and need to convert it into 2 columns, by alternating each row:

1

2

3

4

5

want to convert to:

1
2

3
4

5
6

I've seen a previous post from 2007 where someone asked for a formula to do the reverse of this. 'Domenic' provided a formula =INDEX($A$2:$B$6,INT((ROWS(D$2:D2)-1)/2)+1,MOD(ROWS(D$2:D2)-1,2)+1) which converted

a
1

b
2

c
3

d
4

[code]....

how to reverse this formula?