The sum of 100 consecutive natural numbers is 8450. Take the 1st, 3rd, 5th, ..., 99th (all odd numbers), and add 50 numbers. What is the sum?
100个连续自然数的和是8450，取其中第1个，第3个，第5个，…，第99个(所有的奇数个)，再把50个数相加，和是多少．
<gadget id="calculator">8_450 - 50</gadget>
<output>8_400</output>

<gadget id="calculator">8_400 / 2</gadget>
<output>4_200</output>

<result>4_200</result>