turtle column builders

lenght={ ... }

function placeCollumn()
    turtle.placeUp()
    turtle.placeDown()
    turtle.back()
    turtle.place()
end

shell.run("refuel","all")
turtle.select(2)

function mainProgram()
    if lenght~=nil then
        lenght=tonumber(lenght[1])
        turtle.turnLeft()
        turtle.turnLeft()
        turtle.up()
        for i=1,lenght do
            repeat
                count=turtle.getItemCount(turtle.getSelectedSlot())
                if count<=0 then
                    turtle.select(turtle.getSelectedSlot()+1)
                end
            until count>0
            placeCollumn()
        end
    end
end

mainProgram()