How to identify duplicate values in two columns in Openoffice Calc

Question

I have two columns that have numbers in them. The other has the numbers only once, when the other has duplicates. The numbers in these columns don't match. I need to find all the numbers in column B that have a match in column A.

This probably explains it better:
A B
1 2
2 2
4 5
6 5
7 6
8 6

I want to get a result like:
A B C
1 2 1
2 2 1
4 5 0
6 5 0
7 6 1
8 6 1

or any other way for me to identify the cells in column B which don't have a match in column A

I've spent hours googling and trying different solutions but no go, so a nudge to the right direction would be appreciated

Thank you

-M

Answer 1

In cell C1 place:

=COUNTIF(A$1:A$6;B1)

And copy down.