Every room in a dormitory building has a number, and the numbers of every two rooms have at least two different numbers in two positions. For example, if there is room 101, there cannot be room 501 and room 171. If there are 1000 room numbers from 000 to 999, how many rooms can this dormitory building have at most?
某宿舍楼的每一个房间都有一个编号，每2间房的编号都至少有2个位置上的数字不同，例如如果有101号房间，就不能有501号房间和171号房间．如果允许使用的房间编号从000到999，共1000种，那么这个宿舍楼最多可以有多少个房间．
<gadget id="calculator">10 * 10</gadget>
<output>100</output>

<result>100</result>