When making a cuboid with 18 cubes whose edge length is 1cm, to make its surface area the smallest, how much should the smallest surface area be?
用棱长为1cm的18个正方体做成长方体时，要使它的表面积最小，问最小表面积应该多大？
<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<gadget id="calculator">9 + 6 + 6</gadget>
<output>21</output>

<gadget id="calculator">21 * 2</gadget>
<output>42</output>

<result>42</result>