A sheep is tied to a stump in the middle of a meadow, and the length of the rope from the stump to the sheep's head is 4 meters. How many square meters of grass can this sheep eat?
一只羊栓在一块草地中央的树桩上，树桩到羊头的绳长是4米．这只羊可以吃到多少平方米地面上的草．
<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

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

<result>50.24</result>