new knitter! how do i tell rs?

[howdythere]

OK, so i'm doing my first pattern. i did a 2x2 rib (one row starting with a K, next starting with a P, etc) for 1.5 inches, and am supposed to end with a rs row. HOW do i know which one is a rs row? I am assuming i should end on an even numbered row but it kinda looks the same to me at this point. Is there an official way to be able to tell this? Thanks for helping a newbie