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i know!
+ S$ c% C! @2 W3 L5.39.217.77:8898when they can have 15 mins discussion.5.39.217.77:8898# M2 b: u5 [0 W/ b  ^
make 1 of them to do a specific job whcih is counting公仔箱論壇7 `: S' |7 p1 t) |7 y
only him can turn on off off the light.* M5 a# l, `* ~8 |/ N8 ?
Basically, if you are the first time to get in the room, turn on the light,
$ i9 _  D% V/ T- _" jtvb now,tvbnow,bttvbthen wait for "the special man" to turn the light off....2 t  Z6 j- g& J( o% r2 ]6 g1 Y
when "the special man" count in up to 30 (included himself)' Q1 M2 [( }8 {4 `9 O& t
then it is done!