1999+1998-1997-1996+1995+1994-1993-1992+1991+1990.
1999+1998-1997-1996+1995+1994-1993-1992+1991+1990．
<gadget id="calculator">1_998 - 1_997 - 1_996</gadget>
<output>-1_995</output>

<gadget id="calculator">1_994 - 1_993 - 1_992</gadget>
<output>-1_991</output>

<gadget id="calculator">1_999 + (-1_995) + 1_995 + (-1_991) + 1_991 + 1_990</gadget>
<output>3_989</output>

<result>3_989</result>