A circular cardboard has an outer circumference of 25.12 cm and an inner radius of 1 cm. Find the area of the circular cardboard.
一个圆环形的纸板，外圆周长25.12厘米，内圆半径1厘米，求圆环形纸板的面积．
<gadget id="calculator">25.12 / 3.14 / 2</gadget>
<output>4</output>

<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

<gadget id="calculator">1 ** 2</gadget>
<output>1</output>

<gadget id="calculator">16 - 1</gadget>
<output>15</output>

<gadget id="calculator">3.14 * 15</gadget>
<output>47.1</output>

<result>47.1</result>