In the Tang Dynasty of our country, there was a bronze mirror with "outer square and inner circle" (that is, there is a largest square inside a circular bronze mirror). The radius of a picture of this kind of bronze mirror is 4 cm, so the outer circle of this bronze mirror is the same as the inner square. What is the area in square centimetres.
我国唐代有"外方内圆"的铜镜(即圆形铜镜内有一个最大的正方形)，一个这种铜镜图形的半径是4厘米，则这个铜镜外面的圆与内部的正方形之间的面积是多少平方厘米．
<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

<gadget id="calculator">3.14 * 16</gadget>
<output>50.24</output>

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

<gadget id="calculator">4 * 2 * 4</gadget>
<output>32</output>

<gadget id="calculator">50.24 - 32</gadget>
<output>18.24</output>

<result>18.24</result>