2017-07-06 15:58
258
0
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1 21 20 18 15 11 —
A 4 B 6 C 8
2
A,120。B,135。C,
3
a b
a d d c
c
A,a B b C,c ,D d
4
A B C D
5
A
B ,C
D
6
A1 B 3C 5D 7E 11
F 13 G15 H,17