rope encloses a square with a side length of 1.57 meters. If this rope is used to enclose a circle, what is the maximum area of the circle in square meters?
一根绳子围成一个边长是1.57米的正方形，如果用这根绳子改围一个圆，这个圆的面积最大是多少平方米？
<gadget id="calculator">4 / 3.14 / 2</gadget>
<output>0.636943</output>

<gadget id="calculator">1.57 * 0.636943</gadget>
<output>1.000001</output>

<gadget id="calculator">1.000001 ** 2</gadget>
<output>1.000002</output>

<gadget id="calculator">3.14 * 1.000002</gadget>
<output>3.140006</output>

<result>3.140006</result>