Scroll wheel tool change broken, can someone help? [closed]

Can someone tell me whats wrong with this fix and possibly fix it. I did not make this script btw but I really need it to work. It's supposed to cycle through tools with use of scroll wheel. The forward wheel works with switching weapons, but the scrollwheel back unequips all tools and doesn't equip a new one.

local player = game.Players.LocalPlayer
local char = player.Character or player.CharacterAdded:wait()
game:GetService("UserInputService").InputChanged:connect(function(iO,gPE)
    if not gPE then
        if iO.UserInputType == Enum.UserInputType.MouseWheel then
            print(iO.Position.Z)
            local LastTool = nil
            local Pos = 1
            for i,v in pairs(char:GetChildren())do
                if v:IsA'Tool'then
                    LastTool = v
                end
            end
            char.Humanoid:UnequipTools()
            for i,v in pairs(player.Backpack:GetChildren())do
                if v==LastTool then
                    Pos = i
                end
            end
            if iO.Position.Z == 1 then
                if Pos == 1 then
                    Pos = #player.Backpack:GetChildren()
                    char.Humanoid:EquipTool(player.Backpack:GetChildren()[Pos])
                    wait()
                else
                    Pos = Pos-1
                    char.Humanoid:EquipTool(player.Backpack:GetChildren()[Pos])
                    wait()
                end
            elseif iO.Position == -1 then
                if Pos == #player.Backpack:GetChildren() then
                    Pos = 1
                    char.Humanoid:EquipTool(player.Backpack:GetChildren()[Pos])
                    wait()
                else
                    Pos = Pos+1
                    char.Humanoid:EquipTool(player.Backpack:GetChildren()[Pos])
                    wait()
                end
            end
        end
    end
end)