How many different four-digit numbers can be formed with four number cards of 1,9,9,5? (9 can be used upside down as 6).
用1,9,9,5四个数字卡片，可以组成多少个不同的四位数？(其中9可以倒过来当6用)．
<gadget id="calculator">3 + 3 + 6</gadget>
<output>12</output>

<gadget id="calculator">4 * 6</gadget>
<output>24</output>

<gadget id="calculator">12 + 12 + 24</gadget>
<output>48</output>

<result>48</result>