abcnow

三个红色和两个黑色
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最后那个说我不知道我戴什么颜色帽子.
5 `/ a/ n0 c. ~; x. ftvb now,tvbnow,bttvb- the front #1 , #2 must not be black/black.  Otherwise, #3 will know he is red.  #1/#2 must be red/red or red/black or black/red.
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% l( c+ f& B+ v" L: Ytvb now,tvbnow,bttvb中间那个说我也不知道我戴什么颜色帽子.
2 o6 ]( C1 S( Dtvb now,tvbnow,bttvb- for #2, if he see #1 wearing black, he can be sure he is red.  since #2 cannot be sure, then #1 must NOT be wearing black.
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但是第一个说我知道我戴什么颜色帽子.
; F% E2 l3 K8 d( r# t$ N- #1 must be wearing RED