Simple calculation: 1+2+3+4-5-6-7-8+9+10+11+12-13-14-15-16+…+993+994+995+996-997-998-999 -1000+1001+1002+1003+1004.
简算：1+2+3+4-5-6-7-8+9+10+11+12-13-14-15-16+…+993+994+995+996-997-998-999-1000+1001+1002+1003+1004．
<gadget id="calculator">1_004 - 997 - 998 - 999 - 1_000</gadget>
<output>-2_990</output>

<gadget id="calculator">1_001 + 1_002 + 1_003 + (-2_990)</gadget>
<output>16</output>

<gadget id="calculator">16 * 125</gadget>
<output>2_000</output>

<gadget id="calculator">10 + 2_000</gadget>
<output>2_010</output>

<result>2_010</result>