(1+3+5+...+1997)-(2+4+6+...+1994+1996)=how much.
(1+3+5+…+1997)-(2+4+6+…+1994+1996)=多少．
<gadget id="calculator">1_997 + 1</gadget>
<output>1_998</output>

<gadget id="calculator">1_997 - 1</gadget>
<output>1_996</output>

<gadget id="calculator">1_996 / 2</gadget>
<output>998</output>

<gadget id="calculator">998 + 1</gadget>
<output>999</output>

<gadget id="calculator">999 / 2</gadget>
<output>999/2 = around 499.5</output>

<gadget id="calculator">1_998 * (999/2)</gadget>
<output>998_001</output>

<gadget id="calculator">1_996 + 2</gadget>
<output>1_998</output>

<gadget id="calculator">1_996 - 2</gadget>
<output>1_994</output>

<gadget id="calculator">1_994 / 2</gadget>
<output>997</output>

<gadget id="calculator">997 + 1</gadget>
<output>998</output>

<gadget id="calculator">998 / 2</gadget>
<output>499</output>

<gadget id="calculator">1_998 * 499</gadget>
<output>997_002</output>

<gadget id="calculator">998_001 - 997_002</gadget>
<output>999</output>

<result>999</result>