Counting A Column Uniquely Based On Another Column

I have a column (A) which I use check (ü) or false (û) ─ Wingdings font ─ to indicate whether people from column (C) are joined in group or not.

There are duplicates in the column (C), which I write people's names in, hence there are duplicate checks (ü) or falses (û) in column (A).

I want to count checks (ü) or falses (û) without duplicate, based on column (C); since obviously every checks (ü) or falses (û) would be duplicated multiple times because they have no distinction like names!

I already have a formula for counting column (C) without duplicate which I share below:
=SUM(IF(FREQUENCY(IF(LEN(a2:a497)>0,MATCH(a2:a497,a2:a497,0),""),IF(LEN(a2:a497)>0,MATCH(a2:a497,a2:a497,0),""))>0,1))