Add all the 1000 natural numbers from 1 to 1000, what is the sum?
把从1-1000这1000个自然数所有数字相加，和是多少．
<gadget id="calculator">1 + 9</gadget>
<output>10</output>

<gadget id="calculator">9 / 2</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">10 * (9/2) * 100 * 3</gadget>
<output>13_500</output>

<gadget id="calculator">13_500 + 1 + 0 + 0 + 0</gadget>
<output>13_501</output>

<result>13_501</result>