What is the sum of all odd numbers from 1 to 1999?
从1到1999的所有奇数的和是多少．
<gadget id="calculator">1 + 1_999</gadget>
<output>2_000</output>

<gadget id="calculator">1_000 / 2</gadget>
<output>500</output>

<gadget id="calculator">2_000 * 500</gadget>
<output>1_000_000</output>

<result>1_000_000</result>