I used this to solve my problem:
user_id:(a c)
Found the solution here: Can Users be queried in bulk? E.g. Find users in this list of emails? - #2 by MerrickClark
I used this to solve my problem:
user_id:(a c)
Found the solution here: Can Users be queried in bulk? E.g. Find users in this list of emails? - #2 by MerrickClark