There are 26 consecutive natural numbers. If the sum of the first 13 numbers is 247, what is the sum of the last 13 numbers?
有26个连续的自然数，如果前13个数的和是247，那么后13个数的和是多少．
<gadget id="calculator">13 * 13</gadget>
<output>169</output>

<gadget id="calculator">247 + 169</gadget>
<output>416</output>

<result>416</result>