There is a cuboid iron box containing biscuits, the bottom is square, the side length of the bottom is 20 cm, and the height is 30 cm. The iron box is covered with trademarks all around. What is the area of the trademark in square centimeters?
有一个装饼干的长方体铁盒，底面是正方形，底面边长是20厘米，高是30厘米．这个铁盒的四周印满商标．商标的面积是多少平方厘米？
<gadget id="calculator">20 * 4 * 30</gadget>
<output>2_400</output>

<result>2_400</result>