((1+2*1)/500)+((3+2*2)/500)+((5+2*3)/500)+...+((999+2*500)/500).
((1+2*1)/500)+((3+2*2)/500)+((5+2*3)/500)+…+((999+2*500)/500)．
<gadget id="calculator">1 + 999</gadget>
<output>1_000</output>

<gadget id="calculator">1_000 / 2 / 2</gadget>
<output>250</output>

<gadget id="calculator">1_000 * 250</gadget>
<output>250_000</output>

<gadget id="calculator">1 + 500</gadget>
<output>501</output>

<gadget id="calculator">500 / 2</gadget>
<output>250</output>

<gadget id="calculator">2 * 501 * 250</gadget>
<output>250_500</output>

<gadget id="calculator">250_000 + 250_500</gadget>
<output>500_500</output>

<gadget id="calculator">500_500 / 500</gadget>
<output>1_001</output>

<result>1_001</result>