A school performs gymnastics, and the students of Class 51 are arranged in a 5*5 square formation. How many students are there in the outermost layer of the whole square formation?
某学校进行体操表演，五一班的同学排成5*5的方阵，则整个方阵的最外层一共有多少名同学．
<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<gadget id="calculator">20 - 4</gadget>
<output>16</output>

<result>16</result>