EVENT
BOARDSIZE 19
SETUP W C16 E17 N17 N15 N13 Q10 Q11 R10 Q9 N3 P3 Q3 B4 B3 C7 C10 
SETUP B H17 L17 L15 L13 Q17 R15 R13 P10 R9 R8 R5 P4 O4 D4 C3 G3 
COM
Problem 15. Black to play.  

The white stones in the upper right are still eyeless. How should
Black attack them ? 
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B 1 O14
USER
CORRECT ANSWER
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COM
Correct Answer.

Black first peeps with 1, then ...
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W 2 N14
B 3 P12
COM
... makes a shoulder hit with 3 to split White into two groups.
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W 4 P11
COM
If White 4, ...
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  VAR
  W 4 N11
  MARK 3@P12
  COM
  Variation.

  In answer to Black 3, White might immediately jump out to 4.
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  B 5 P11
  W 6 Q8
  B 7 R7
  W 8 O8
  COM
  The sequence continues to White 8, but ... 
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  B 9 N10
  MARK B@N4 8@O8 A@O9
  COM
  ... Black leans on the white group at the top by attaching with
  9. If White 8 at A, Black will still attach at 9. If Black needs
  more strength to attack the white group on the right, Black can
  also lean on the white group at the bottom with the forcing move
  at B.
  <=
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  ENDVAR
B 5 O12
COM
... Black extends to 5, leaving White with two isolated and eyeless
groups. If White tries to save one of then, the other will fall.
This is a good example of a double attack.
<=
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