A circular flower bed with a diameter of 8 meters is paved with a 1-meter-wide cement road around it. What is the area of this concrete road in square meters?
一个直径是8米的圆形花坛，在它的外围铺设1米宽的水泥路．这条水泥路的面积是多少平方米？
<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">3.14 * 25</gadget>
<output>78.5</output>

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

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

<gadget id="calculator">78.5 - 50.24</gadget>
<output>28.26</output>

<result>28.26</result>