Among the fifty natural numbers 1949, 1950, 1951, ... 1997, 1998, how much more is the sum of all even numbers than the sum of all odd numbers?
在1949，1950，1951，…1997，1998这五十个自然数中，所有偶数之和比所有奇数之和多多少？
<gadget id="calculator">1_950 + 1_998</gadget>
<output>3_948</output>

<gadget id="calculator">25 / 2</gadget>
<output>25/2 = around 12.5</output>

<gadget id="calculator">3_948 * (25/2)</gadget>
<output>49_350</output>

<gadget id="calculator">1_949 + 1_997</gadget>
<output>3_946</output>

<gadget id="calculator">3_946 * (25/2)</gadget>
<output>49_325</output>

<gadget id="calculator">49_350 - 49_325</gadget>
<output>25</output>

<result>25</result>