@hawkgettds Being a math prof, I was curious as to what “Concrete Math” is , since it is nonstandard terminology. So I googled the course and found the course description at an elite high school. Interesting stuff - it’s a solid college level discrete math course; graph theory, reg exps and more. If that’s offered, maybe take that?
It seems the OP is missing the forest for the trees - it is one course in one semester - do AO’s really have the time to dig deep into this? Since OP is from an elite high school, wouldn’t AO’s at elite universities be looking for stuff beyond a rigorous course list from a such a student(which is assumed). Projects or competitive CS or math competitions etc. and stuff of that ilk. If OP has those types of credentials, I think that would trump one or two elective one-semester courses in senior year.
On a separate note - OP mentioned earlier that they will submit first semester grades for the RD schools they’re applying to. CS is a limited enrollment program in many universities they probably consider as “safeties” , like UMD. So maybe get some EA’s into those schools as backups.