There is a circular path beside the flower bed in the park. The diameter of the flower bed is 40m, and the width of the path is 1m. The garden workers need to lay stones on the circular path. How many square meters is the area of the stone paving?
公园的花坛边有一条环形小路，花坛直径是40m，小路宽1m，园林工人要在环形小路上面铺石子，铺石子的面积是多少平方米？
<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">20 + 1</gadget>
<output>21</output>

<gadget id="calculator">21 ** 2</gadget>
<output>441</output>

<gadget id="calculator">20 ** 2</gadget>
<output>400</output>

<gadget id="calculator">441 - 400</gadget>
<output>41</output>

<gadget id="calculator">3.14 * 41</gadget>
<output>128.74</output>

<result>128.74</result>