piece of square paper with a side length of 2 decimeters, from which the largest circle is cut, what is the utilization rate of this paper.
一张边长为2分米的正方形纸，从中剪一个最大的圆，这张纸的利用率是多少．
<gadget id="calculator">2 / 2</gadget>
<output>1</output>

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

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

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">100 / 100</gadget>
<output>1</output>

<gadget id="calculator">3.14 * (1/4) * 1</gadget>
<output>0.785</output>

<result>0.785</result>