How can I set my vlookup to pull the next number in the list?

I want to setup a vlookup that will pull over 1 of each number in a given data set. See below for example.

Example:
A|B
1|3
1|7
2|8
3|1
3|2
3|2
3|9

=vlookup(3,$A$1:$B$6,2,false)
This will result with the value of 1, which is needed for the first input, but after that, I want the next formula in the cell underneath it to display 2 and then the formula in the cell beneath that to display 9 (instead of 2 again). Is there anyway I can set this up in excel? Any help on this is much appreciated!

EDIT: I was able to solve this with: =INDEX($A$2:$A$8,MATCH(0,INDEX(COUNTIF($B$1:B1,$A$2:$A$8),0,0),0))

Thanks for posting the solution. In future, you can post the solution in post 2 so its clear to others which is the question and which is the solution.