A performance square has 7 people in each row. There are 7 rows. How many people are there in the outermost layer?
一个表演方阵，每排7人，有7行，最外层有多少人．
<gadget id="calculator">7 * 4</gadget>
<output>28</output>

<gadget id="calculator">28 - 4</gadget>
<output>24</output>

<result>24</result>