After a miniature projectile explodes, its effective killing radius is 20 meters. What is the killing area.
一种微型炮弹爆炸后，有效的杀伤半径是20米．杀伤面积是多少．
<gadget id="calculator">20 ** 2</gadget>
<output>400</output>

<gadget id="calculator">3.14 * 400</gadget>
<output>1_256</output>

<result>1_256</result>