Divide a cuboid with red on its surface into several small cubes with a volume of 1 cubic centimeter. Among them, there are only 7 small cubes without any red. What is the volume of the original cuboid?
将一个表面图有红色的长方体分割成若干个体积为1立方厘米的小正方体，其中一点红色都没有的小正体只有7块，原来长方体的体积是多少立方厘米？
<gadget id="calculator">7 + 2</gadget>
<output>9</output>

<gadget id="calculator">1 + 2</gadget>
<output>3</output>

<gadget id="calculator">9 * 3 * 3</gadget>
<output>81</output>

<result>81</result>