For a cube whose edge length is 3, hollow out the upper, lower, front, rear, and middle cubes, and ask for the surface area of the figure.
一个棱长为3的正方体，将上下前后的最中间的正方体挖空，问此图形的表面积．
<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<gadget id="calculator">9 - 1</gadget>
<output>8</output>

<gadget id="calculator">8 * 4</gadget>
<output>32</output>

<gadget id="calculator">3 * 3 * 2</gadget>
<output>18</output>

<gadget id="calculator">32 + 18</gadget>
<output>50</output>

<gadget id="calculator">1 * 1 * 4 * 4</gadget>
<output>16</output>

<gadget id="calculator">1 * 1 * 2</gadget>
<output>2</output>

<gadget id="calculator">16 + 2</gadget>
<output>18</output>

<gadget id="calculator">50 + 18</gadget>
<output>68</output>

<result>68</result>