If a square cardboard with a side length of 2 decimeters is cut into the largest circle, how many square decimeters need to be cut?
把一块边长为2分米的正方形纸板剪成一个最大的圆，需要剪去的面积是多少平方分米？
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

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

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

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

<gadget id="calculator">4 - 3.14</gadget>
<output>0.86</output>

<result>0.86</result>