(2+5+8+...+2000)-(1+4+7+...+1999)=how much.
(2+5+8+…+2000)-(1+4+7+…+1999)=多少．
<gadget id="calculator">2 + 2_000</gadget>
<output>2_002</output>

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

<gadget id="calculator">1_998 / 3</gadget>
<output>666</output>

<gadget id="calculator">666 + 1</gadget>
<output>667</output>

<gadget id="calculator">667 / 2</gadget>
<output>667/2 = around 333.5</output>

<gadget id="calculator">2_002 * (667/2)</gadget>
<output>667_667</output>

<gadget id="calculator">1 + 1_999</gadget>
<output>2_000</output>

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

<gadget id="calculator">2_000 * (667/2)</gadget>
<output>667_000</output>

<gadget id="calculator">667_667 - 667_000</gadget>
<output>667</output>

<result>667</result>