A sheep is tied to a 5-meter-long rope and tied to a tree stump in the middle of the grass. What is the maximum area the sheep grazes in square meters?
一根长5米的绳子系着一只羊，栓在草地中央的树桩上，羊吃草的面积最多是多少平方米？
<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">3.14 * 25</gadget>
<output>78.5</output>

<result>78.5</result>