If a circular piece of paper is cut into two equal semicircles, their circumference is increased by 8 cm, what is the area of the circle in square centimeters?
把一个圆形纸片剪成两个相等的半圆，它们的周长增加了8厘米，这个圆的面积是多少平方厘米．
<gadget id="calculator">8 / 2 / 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>