If a square plank with a perimeter of 8 decimeters is processed into the largest circle, how many square decimeters is the leftover material after processing?
把一块周长是8分米的正方形木板加工成一个最大的圆，加工成后的边角料是多少平方分米？
<gadget id="calculator">8 / 4</gadget>
<output>2</output>

<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>