How many square centimeters of cardboard are needed to make a matchbox with a length of 5 cm, a width of 3 cm, and a height of 1 cm (not counting the thickness of the inner wall)?
做一个长是5厘米，宽是3厘米，高是1厘米的火柴盒(内壁厚度不计)，需要多少平方厘米的硬纸板？
<gadget id="calculator">15 + 5 + 3</gadget>
<output>23</output>

<gadget id="calculator">23 * 2</gadget>
<output>46</output>

<result>46</result>