In a piece of grassland, a sheep is tied to a 4-meter-long rope to graze on the grassland. What is the maximum area of grass that the sheep can eat?
一块草地，用一根长4米的绳拴住一只羊到草地上吃草，羊最多能吃到多少面积的草？
<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

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

<result>50.24</result>