In a square of cardboard with a side length of 4 decimeters, how many square decimeters of cardboard are left after cutting off the largest circle.
在边长为4分米的正方形硬纸板中，截去一个最大的圆后，还剩下多少平方分米的硬纸板．
<gadget id="calculator">4 * 4</gadget>
<output>16</output>

<gadget id="calculator">4 / 2</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">16 - 12.56</gadget>
<output>3.44</output>

<result>3.44</result>