31*128-28*31.
31*128-28*31．
<gadget id="calculator">31 * 128</gadget>
<output>3_968</output>

<gadget id="calculator">28 * 31</gadget>
<output>868</output>

<gadget id="calculator">3_968 - 868</gadget>
<output>3_100</output>

<result>3_100</result>