The difference between two four-digit numbers is 1996. We call such two four-digit numbers a number pair, such as 3210 and 1214, 8059 and 6063, etc. Find how many pairs of such numbers there are.
有两个四位数的差为1996，我们把这样的两个四位数称为一个数对，像3210和1214，8059和6063等．求这样的数对一共有多少对．
<gadget id="calculator">9_999 - 2_996</gadget>
<output>7_003</output>

<gadget id="calculator">7_003 + 1</gadget>
<output>7_004</output>

<result>7_004</result>