function is_changing(slot)
  count = turtle.getItemCount(slot)
  if count == 0 then
    return true
  end

  sleep(1)

  newCount = turtle.getItemCount(slot)
  return count ~= newCount
end

while true do
  for i=1,16 do
    if not is_changing(i) then
      turtle.select(i)
      turtle.dropUp()
    end
  end
  sleep(0.1)
end