How many square centimeters of leftovers are left after cutting the largest circle out of a plastic sheet 30 cm long and 20 cm wide?
用一块长30厘米，宽20厘米的塑料片剪一个最大的圆后，剩下多少平方厘米的边角料？
<gadget id="calculator">30 * 20</gadget>
<output>600</output>

<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">3.14 * 100</gadget>
<output>314</output>

<gadget id="calculator">600 - 314</gadget>
<output>286</output>

<result>286</result>