1+2-3-4+5+6-7-8+...+2001+2002-2003-2004+2005+2006-2007-2008+2009=how much.
1+2-3-4+5+6-7-8+…+2001+2002-2003-2004+2005+2006-2007-2008+2009=多少．
<gadget id="calculator">(-4) * 502</gadget>
<output>-2_008</output>

<gadget id="calculator">(-2_008) + 2_009</gadget>
<output>1</output>

<result>1</result>