Billiards, 11 characters = 17 bytes
⇲ ⇲ + 1 + ↥ Implements x + y + 1. Pretty elementary. It takes the inputs on two separate lines. (By the way, the language was modified slightly after the challenge, but only to suppress the prompt from inputting, not sure if this answer is still valid).
7 characters = 11 bytes, non-competing
This one is shorter but only possible after a new update of the language:
⇲ ⇲ = $ This uses x == y, which was shamelessly stolen from @ATaco's RProgN solution [ hope you don't mind (: ]. The $, on exit, outputs how many balls passed over it.