Find overbooked rooms

Hi,

I want to create a measure that gives me overbookings. 

The table looks like this:

RoomID                  Date                 TypeRoom

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

1                             2018-06-15      4
2                             2018-06-15      6
3                             2018-06-15      6
1                             2018-06-16      4
2                             2018-06-15      6
3                             2018-06-18      6
1                             2018-06-17      4
2                             2018-06-15      6
3                             2018-06-18      6

 In the table abow the measure should return 2  .
RoomId = 2 is overbooked 2018-06-15 ( three bookings)
and RoomID = 3 is overbooked 2018-06-18.  (two bookings)
Any idea of how this could be done?