How to select all bottom elements?

Question

css

There are N number of divs in the container, let's say 6, flexed at 3 per line, as an example: sandbox
Need to make a rule that selects 4, 5 and 6 divs (i.e. the last ones) so that I can set their properties. There can be up to 12 divs. Their current number is in a variable.
It would be possible, on the contrary, to select all but the last ones.

Answer 1

jsbin.com/ufosox/1/edit?html,css,output
PS Not my solution