With the four numbers 5, 6, 7, and 8, many four-digit numbers without repeated numbers can be formed. What is the sum of all these four-digit numbers?
用5、6、7、8这四个数可以组成许多没有重复数字的四位数，所有这些四位数的和是多少．
<gadget id="calculator">5 + 6 + 7 + 8</gadget>
<output>26</output>

<gadget id="calculator">26 * 6_666</gadget>
<output>173_316</output>

<result>173_316</result>