Eloqua Insight - distinct column email address?

Which function, and how exactly should I use it, in order to return only unique email addresses in an Insight Reporting report for a given time range?
Currently, I use Campaing Analysis with the Email Address column that contains the same addresses multiple times, and I would like to restrict the report so that each email appears only once.

I tried to add formula to Email Address column but I still see duplicates of emails there.

DISTINCT("Email Address")