Around a circular flower pond with a diameter of 4 meters, a gravel road with a width of 1 meter is paved. What is the area of the gravel road in square meters?
在直径是4米的圆形花池周围，铺了1米宽的石子路，这个石子路的面积是多少平方米．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">1 + 2</gadget>
<output>3</output>

<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

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

<gadget id="calculator">9 - 4</gadget>
<output>5</output>

<gadget id="calculator">3.14 * 5</gadget>
<output>15.7</output>

<result>15.7</result>