A ring, the radius of the inner circle is 1dm, the width of the ring is 1dm, what is the area of the ring in dm**2.
一个圆环，内圆半径是1dm，环宽1dm，圆环的面积是多少dm**2．
<gadget id="calculator">1 + 1</gadget>
<output>2</output>

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

<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<gadget id="calculator">1 ** 2</gadget>
<output>1</output>

<gadget id="calculator">3.14 * 1</gadget>
<output>3.14</output>

<gadget id="calculator">12.56 - 3.14</gadget>
<output>9.42</output>

<result>9.42</result>