It is known that x**2=10, then how much is 3.14x**2-0.4=.
已知x**2=10，则3.14x**2-0.4=多少．
<gadget id="calculator">3.14 * 10</gadget>
<output>31.4</output>

<gadget id="calculator">31.4 - 0.4</gadget>
<output>31</output>

<result>31</result>