square block of wood with side length 3 cm is cut out in the center of each face with a square column hole with side length 1 cm. What is the remaining volume in cubic centimeters?
一个棱长是3厘米的正方体木块，各面中心凿出一孔面边长是1厘米的正方形柱孔，它余下的体积是多少立方厘米？
<gadget id="calculator">3 * 3 * 3</gadget>
<output>27</output>

<gadget id="calculator">1 * 1 * 1 * 6</gadget>
<output>6</output>

<gadget id="calculator">27 - 6</gadget>
<output>21</output>

<result>21</result>