1993*1993+1992*1992-1993*1992-1992*1991=how much.
1993*1993+1992*1992-1993*1992-1992*1991=多少．
<gadget id="calculator">1_993 * 1_993</gadget>
<output>3_972_049</output>

<gadget id="calculator">1_992 * 1_992</gadget>
<output>3_968_064</output>

<gadget id="calculator">1_993 * 1_992</gadget>
<output>3_970_056</output>

<gadget id="calculator">1_992 * 1_991</gadget>
<output>3_966_072</output>

<gadget id="calculator">3_968_064 - 3_970_056 - 3_966_072</gadget>
<output>-3_968_064</output>

<gadget id="calculator">3_972_049 + (-3_968_064)</gadget>
<output>3_985</output>

<result>3_985</result>