Use 2 four-digit numbers composed of 8 numbers 1, 2, 3, 4, 6, 7, 8, 9 to minimize the difference between these two numbers (big reduction). What is the minimum difference?
用1、2、3、4、6、7、8、9这8个数组成的2个四位数，使这两个数的差最小(大减小)，这个差最小是多少？
<gadget id="calculator">4_126 - 3_987</gadget>
<output>139</output>

<result>139</result>