How do I stop the same map from being chosen twice?

I have made an effort to try and figure it out and I can't. I'm hoping someone will be able to help me else I'll be stuck on this problem for awhile.

Here is the code. Does anyone have any suggestions to stop it from choosing the same map twice in a row?

function chooseMap()					--Chooses Map (IN-PROGRESS)
	local mapChoice = math.random(1,3)
		if mapChoice == 1 then
			print("Map 1 got chosen!")
				local map = game.ServerStorage.Maps.Map1:clone()
				map.Parent = game.Workspace
				map:MoveTo(Vector3.new(100,100,100))
			--load map 1
		elseif mapChoice == 2 then
			print("Map 2 got chosen!")
				local map = game.ServerStorage.Maps.Map2:clone()
				map.Parent = game.Workspace
				map:MoveTo(Vector3.new(100,100,100))
			--load map 2
		elseif mapChoice == 3 then
			print("Map 3 got chosen!")
				local map = game.ServerStorage.Maps.Map3:clone()
				map.Parent = game.Workspace
				map:MoveTo(Vector3.new(100,100,100))
			--load map 3
	end	
end