Calculation: 1+2-3-4+5+6-7-8+...+1994-1996+1997+1998-1999-2000+2001.
计算：1+2-3-4+5+6-7-8+…+1994-1996+1997+1998-1999-2000+2001．
<gadget id="calculator">1_993 - 1_994 - 1_996</gadget>
<output>-1_997</output>

<gadget id="calculator">(-1_997) + 1_997</gadget>
<output>0</output>

<gadget id="calculator">1_998 - 1_999 - 2_000</gadget>
<output>-2_001</output>

<gadget id="calculator">(-2_001) + 2_001</gadget>
<output>0</output>

<gadget id="calculator">1 + 0 + 0</gadget>
<output>1</output>

<result>1</result>