The students participated in the group gymnastics performance and formed a square formation. There are 18 people standing on each side of the outermost layer, how many people are there in total on the outermost layer?
同学们参加团体操表演，排成方阵．最外层每边站18人，最外层一共要有多少人？
<gadget id="calculator">18 * 4</gadget>
<output>72</output>

<gadget id="calculator">72 - 4</gadget>
<output>68</output>

<result>68</result>