How to make this script do the opposite of what it is supposed to do?

This script is supposed to make wheels turn.. I tried making the wheels on the back of a bus go the opposite way.. but I couldn't figure out how.. the game on my profile shows the bus I was trying to do it with.

local m = Instance.new("Motor")
m.MaxVelocity = 0.05
m.Part0 = script.Parent
m.Part1 = script.Parent.Parent.Part
m.Parent = script.Parent

local seat = script.Parent.Parent.Parent.VehicleSeat

seat.Changed:connect(function()
    if seat.Steer == 0 then
        m.DesiredAngle = 0
    elseif seat.Steer == 1 then
        m.DesiredAngle = -1/3
    elseif seat.Steer == -1 then
        m.DesiredAngle = 1/3
    end
end)

The bus is not finished..