How to make a seat that only first person who sat can sit in?

I'm making a car game and I want to make a script that will jump someone if they weren't the first person to sit in the car. How do I do that?

Try this:

local car = script.Parent
local seat = car.Seat
local playerwhosatfirst

seat:GetPropertyChangedSignal('Occupant'):Connect(function(hum)
	if not playerwhosatfirst then
		playerwhosatfirst = game.Players:GetPlayerFromCharacter(hum.Parent)
	elseif playerwhosatfirst and playerwhosatfirst ~= game.Players:GetPlayerFromCharacter(hum.Parent) then
		hum.Jump = true
	end
end)