Dig a fountain with a radius of 1.5 meters in the middle of a circular lawn with a circumference of 31.4 meters. How many square meters of grass are left?
在一块周长为31.4米的圆形草地中间挖一个半径为1.5米的喷水池，草地还剩下多少平方米？
<gadget id="calculator">31.4 / 3.14 / 2</gadget>
<output>5</output>

<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">3.14 * 25</gadget>
<output>78.5</output>

<gadget id="calculator">1.5 ** 2</gadget>
<output>2.25</output>

<gadget id="calculator">3.14 * 2.25</gadget>
<output>7.065</output>

<gadget id="calculator">78.5 - 7.065</gadget>
<output>71.435</output>

<result>71.435</result>