What's a simplest way to get -5v from +/-12v?

Hi! I'm working on an arduino project that has a -12v/0v/+12 psu. +12 is fed directly into arduinos voltage regulator, so there's also a +5v line available. I need to convert a -5v+5v signal to 0v+5v to feed it into arduinos analogue input and I've already mocked up a schematic in circuitjs based on an opamp that seems to do what I want. The only problem is that it needs -5v to shift the signal to be unipolar. I know that I can invert +5v using another opamp, but maybe there's some simpler way? I'd really like to avoid adding another opamp just for this? In this schematic I used simple voltage divider to get the needed voltage, but I guess that's not the best approach?

TLDR: I have -12v, 0v, +12v and +5v, what's the easiest way to get -5v?