1998+1997-1996-1995+1994+1993-1992-1991+...+6+5-4-3+2+1=how much.
1998+1997-1996-1995+1994+1993-1992-1991+…+6+5-4-3+2+1=多少．
<gadget id="calculator">1_998 - 3</gadget>
<output>1_995</output>

<gadget id="calculator">1_995 + 1</gadget>
<output>1_996</output>

<gadget id="calculator">1_996 / 4</gadget>
<output>499</output>

<gadget id="calculator">4 * 499</gadget>
<output>1_996</output>

<gadget id="calculator">1_996 + 2 + 1</gadget>
<output>1_999</output>

<result>1_999</result>