lamb is tied to a 2-meter-long rope (the length of the joint is not counted), please calculate how much grassland the lamb can graze on?
一头小羊拴在一根长2米的绳子上(接头长度不计)，请同学们算一算小羊可以在多大面积的草地上吃草？
<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

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

<result>12.56</result>