sum() of equal Metric/Event values as Dimension

[#1]

I've got an event to count our user logins and I've got another prop/eVar to store the visitor id.

Now I would like to know, how many visitors logged in once, twice, ... within last month.

When I create a report in Discover I get

Visitor ID     Logins

--------------------------

12345                 7

08151                 7

--------------------------

35672                 6

82349                 6

12343                 6

--------------------------

94065                 5

--------------------------

It would be helpful to sum() the login events to get

Sum     Logins

--------------------------

3                6

--------------------------

2                7

--------------------------

1                5

--------------------------