The sum of 18 consecutive natural numbers is 315. So what is the sum of 18 consecutive natural numbers immediately following these 18 numbers?
18个连续的自然数的和是315．那么紧接在这18个数字后面的18个连续的自然数的和是多少？
<gadget id="calculator">18 * 18</gadget>
<output>324</output>

<gadget id="calculator">315 + 324</gadget>
<output>639</output>

<result>639</result>