circular fountain pool with a diameter of 4m is built in the middle of a circular lawn with a radius of 5m. How many square meters is left on the grass?
在一个半径为5m的圆形草地中间修一个直径为4m的圆形喷泉池．这块草地的面积还剩多少平方米？
<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

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

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

<gadget id="calculator">25 - 4</gadget>
<output>21</output>

<gadget id="calculator">3.14 * 21</gadget>
<output>65.94</output>

<result>65.94</result>