1999*1998.1998-1997*1999.1999=how much.
1999*1998.1998-1997*1999.1999=多少．
<gadget id="calculator">1_999 * 1_998.1998</gadget>
<output>3_994_401.4002</output>

<gadget id="calculator">1_997 * 1_999.1999</gadget>
<output>3_992_402.2003</output>

<gadget id="calculator">3_994_401.4002 - 3_992_402.2003</gadget>
<output>1_999.1999</output>

<result>1_999.1999</result>