A cylindrical bucket with a diameter of 4 decimeters is placed on the ground, what is the area occupied by it?
一个圆柱形水桶的直径是4分米，放在地上，它的占地面积为多少．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<result>12.56</result>