❔ Find common substring at start of every string in list

I have a list of Windows path strings and I want to determine the common beginning shared by all of them, if such a thing exists.

So, a list like:

C:\User\hi.txt
C:\User\b.txt
C:\User\hh.txt

C:\User\hi.txt
C:\User\b.txt
C:\User\hh.txt

would output the string

C:\User\

C:\User\

.

How to smoothly accomplish such a thing?