Using the four numbers 8, 6, 3, and 5, how many different four-digit numbers can be formed without repeating numbers.
用8、6、3、5这四个数字，可以组成多少个没有重复数字的不同的四位数．
<gadget id="calculator">4 * 3 * 2 * 1</gadget>
<output>24</output>

<result>24</result>