The students play a game of square formation, boys stand on the outermost layer of the square formation, and there are 6 people on each side. How many boys are needed to play the game?
同学们玩一个方阵游戏，方阵最外层站男孩，每边6人．要玩这个游戏，最外层的男孩共需多少人？
<gadget id="calculator">6 * 4</gadget>
<output>24</output>

<gadget id="calculator">24 - 4</gadget>
<output>20</output>

<result>20</result>