Remove characters from string from the right after 4 characters

Hello,

I have a column of strings as such:

ADJRGST1.0102040042.LST
ADPSL01.T34.0929091855.LST
CARCK11.T2298.0106094338.LST
ILPPR01.T2286.0110103449.LST

Using the first line as an example:
Starting from the right, I need to keep the first 4 characters (.LST), remove the next 11 characters (.0102040042) and keep the rest (ADJRGST1)

So my end result would be ADJRGST1.LST

I feel that it's easy because ALL of my cell strings will have the same character count to keep and remove starting from the right and I'm just struggling to find the correct function syntax.

Any help/guidance would be greatly appreciated.

Thx!
Dave