A cuboid whose base is a square, expands its sides to form a square with a side length of 20 cm. What is the volume of the cuboid?
一个底面是正方形的长方体，把它的侧面展开是一个边长是20厘米的正方形，这个长方体的体积是多少？
<gadget id="calculator">20 / 4</gadget>
<output>5</output>

<gadget id="calculator">5 * 5 * 20</gadget>
<output>500</output>

<result>500</result>