There are three cubes of iron, and their surface areas are 24 square centimeters, 54 square centimeters and 294 square centimeters. Now three pieces of iron are melted into a big cube, find the volume of the big cube.
有三个正方体铁块，它们的表面积分别是24平方厘米、54平方厘米和294平方厘米．现将三块铁熔成一个大正方体，求这个大正方体的体积．
<gadget id="calculator">2 * 2 * 2</gadget>
<output>8</output>

<gadget id="calculator">3 * 3 * 3</gadget>
<output>27</output>

<gadget id="calculator">7 * 7 * 7</gadget>
<output>343</output>

<gadget id="calculator">8 + 27 + 343</gadget>
<output>378</output>

<result>378</result>