There is a tree on the lawn, and a sheep is tied to the tree with a 10-meter-long rope. How big is the grass that the sheep can eat? (Note that the folded end of the rope is not counted)
草坪上有一棵树，用10米长的绳子把一只羊栓在树上，这只羊能吃到草的面积有多大？(注绳子的折头不算)
<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

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

<result>314</result>