1-3+5-7+9-11+...-1995+1997=
1-3+5-7+9-11+…-1995+1997=
<gadget id="calculator">1_997 - 1_995</gadget>
<output>2</output>

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

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

<result>999</result>