To make a gift box in the shape of a cuboid with a length of 40cm, a width and a height of 10cm, how much cardboard should be used at least?
做一个长40cm，宽和高都是10cm的长方体形状的礼品盒，至少用多少硬纸板？
<gadget id="calculator">40 * 10 * 2</gadget>
<output>800</output>

<gadget id="calculator">10 * 10 * 4</gadget>
<output>400</output>

<gadget id="calculator">800 + 400</gadget>
<output>1_200</output>

<result>1_200</result>