Cut out the largest circle on a square lead plate with a side length of 20 cm, what is the area cut out in square centimeters?
在边长是20厘米的正方形铅板上，剪出一个最大的圆，剪去的面积是多少平方厘米．
<gadget id="calculator">20 * 20</gadget>
<output>400</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">400 - 314</gadget>
<output>86</output>

<result>86</result>