A number of students line up in a hollow square with 10 people on each side of the outermost layer, a total of 4 layers, so what is the total number of people in this square?
若干同学排成一个最外层每边10人共4层的中空方阵，那么这方阵的总人数是多少人．
<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">9 * 4</gadget>
<output>36</output>

<result>36</result>