A sheep is tied to a tree. The rope to tie the sheep is 2 meters long. The sheep is surrounded by grass. What is the area in square meters that the sheep can eat the most grass?
树上拴着一只羊，拴羊的绳子长2米，羊的周围全是草，羊能吃到最多的草的面积是多少平方米．
<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

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

<result>12.56</result>