27. n workers load and unload a batch of goods, each with the same loading and unloading speed. If these workers work simultaneously, it will take 12 hours to complete the loading and unloading. Now the loading and unloading method is changed, starting with one person working, and then adding one person every 2 hours, each person who participates in the loading and unloading continues to work until the end, and the last person's loading and unloading time is $\frac{1}{5}$ of the first person's loading and unloading time. Then $n=$ $\qquad$ $-$
$9$