t = peripheral.wrap("top")
frequency = 0
function is_there_item(size)
	for i=1,size do
		if t.getStackInSlot(i) then
			return true
		end
	end
end

while true do
	t.setFrequency(frequency)
	while is_there_item(27) do
		sleep(10)
	end
	frequency = frequency+1
end