Combine the eight numbers 1, 2, 3, 4, 5, 6, 8, and 9 into two four-digit numbers so that the difference between these two numbers is the smallest. What is the difference?
将1、2、3、4、5、6、8、9这八个数组成两个四位数，使这两个数的差最小，这个差是多少．
<gadget id="calculator">5_123 - 4_986</gadget>
<output>137</output>

<result>137</result>