I am aware that this is a soft-question (hence the tag) but feel this question still is warranted in this community.
I'm writing a proof for the circumference of a circle using a line integral. Naturally I'm using $C(r)$ to represent circumference. The problem is that basically every text I've ever seen on line integrals uses the subscript $C$ to represent the curve along which we are integrating. Naturally, I don't want something that looks like this:
$$C(r)=\oint_Cds$$
Is there any common alternative subscript to replace $C$ such that this doesn't confuse a reader? I realise this may seem trivial but it's for a formal textbook and I'd like to use as conventional of notation as possible.