Draw the largest circle in a square with a circumference of 16 cm, what is the area of the circle in square centimeters
在周长是16厘米的正方形内画一个最大的圆，这个圆的面积是多少平方厘米
<gadget id="calculator">16 / 4 / 2</gadget>
<output>2</output>

<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

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

<result>12.56</result>