Showing Common values

1. I have a slicer which has 3 groups Group1 , Group2, Group3.
2. In table there are many users and few users belongs to 2 groups or 3 groups.
3. In the slicer selection if I select group 1 , it will show group 1 users if I select group 1 and 2 it will show all users exist in group 1 and 2 

My requirement/doubt

1. when I choose group 1 and 2 from Slicer, my report should show only users belongs to or present in 1 and 2 both (like show only common users among groups)