324 students form a three-layer hollow square, how many students are there on each side of the outermost layer?
324名同学围成一个三层空心方阵，最外层每边有多少名同学．
<gadget id="calculator">324 / 4 / 3</gadget>
<output>27</output>

<gadget id="calculator">27 + 3</gadget>
<output>30</output>

<result>30</result>