EVENT
BOARDSIZE 19
SETUP W C14 C12 C11 P11 Q11 R11 S9 R13 K17 M16 N16 O17 P17 Q18 Q15 R15 S15 S16 
SETUP B C16 D16 D14 D12 D4 Q4 Q10 P10 O10 O11 Q13 O14 N15 H17 H15 R18 S17 Q17 R16 Q16 P16 O16 
COM
Problem 44. Black to play.  

White's stones at the top right are struggling for life inside
Black's sphere of influence. How should Black attack them ? 
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B 1 M18
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

This is the kind of position in which you want to gauge out the
eyes of your opponent's stones. The placement of Black 1 robs
the white stones of their base and threatens to cut. White's
stones are trapped inside Black's sphere of influence.
Next ...
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  VAR
  B 1 J18
  COM
  Failure.

  Black 1 ...
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  W 2 K18
  B 3 P18
  COM
  ... and 3 are certainly sente, but ...
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  W 4 O18
  COM
  ... so is White 4, ...
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  B 5 Q19
  W 6 M18
  COM
  ... so White can secure two eyes with 6.
  <=
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  ENDVAR
W 2 N18
COM
If White defends against the cut with 2, ...
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  VAR
  W 2 L18
  COM
  Variation.

  White 2 here is another possibility, but ...
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  B 3 O18
  COM
  ... Black takes profit with 3 ...
  ENDCOM
  W 4 N18
  B 5 P18
  COM
  ... and 5.
  ENDCOM
  W 6 N17
  B 7 J18
  COM
  After Black 7, White's group still doesn't have two eyes.
  <=
  ENDCOM
  ENDVAR
B 3 L17
COM
... Black links up with 3 ...
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W 4 L16
B 5 K18
COM
... and 5. White is without eyes, so she must seek life in the
center.
<=
ENDCOM