Dig a reservoir with a depth of 3 meters and a diameter of 4 meters at the bottom. What is the area of the reservoir in square meters?
挖一个深3米，底面直径4米的蓄水池，水池的占地面积是多少平方米．
<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>