If two cubes with side lengths of 3 cm are put together to form a cuboid, what is the reduction in surface area in square centimetres?
棱长是3厘米的两个正方体拼成一个长方体，表面积减少多少平方厘米．
<gadget id="calculator">3 * 3 * 2</gadget>
<output>18</output>

<result>18</result>