During the War of Resistance Against Japan, Wangzhuang militia made a kind of earth mine. When it exploded, the effective killing distance was 15 meters. How many square meters was its effective killing area?
抗日战争时期王庄民兵自制一种土雷，爆炸时，有效杀伤距离是15米，它的有效杀伤面积是多少平方米？
<gadget id="calculator">3.14 * 15 * 15</gadget>
<output>706.5</output>

<result>706.5</result>