What is the sum of two numbers adjacent to 1000?
与1000相邻的两个数的和是多少．
<gadget id="calculator">1_000 - 1</gadget>
<output>999</output>

<gadget id="calculator">1_000 + 1</gadget>
<output>1_001</output>

<gadget id="calculator">999 + 1_001</gadget>
<output>2_000</output>

<result>2_000</result>