How many such four-digit numbers are there (the first and last numbers are not 0), and the difference between two adjacent numbers is 5.
一共有多少个这样的四位数(首尾数字不为0)，它有两个相邻的数字差为5．
<gadget id="calculator">9_999 - 1_000</gadget>
<output>8_999</output>

<gadget id="calculator">8_999 + 1</gadget>
<output>9_000</output>

<gadget id="calculator">9 * 9 * 9 * 9</gadget>
<output>6_561</output>

<gadget id="calculator">9_000 - 6_561</gadget>
<output>2_439</output>

<result>2_439</result>