A cylindrical granary with a base radius of 4 meters, how many square meters does this granary occupy?
一个圆柱形粮仓，底面半径4米，这个粮仓的占地面积是多少平方米？
<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

<gadget id="calculator">3.14 * 16</gadget>
<output>50.24</output>

<result>50.24</result>