EVENT
BOARDSIZE 19
SETUP W C15 F15 C6 Q3 N3 R5 
SETUP B D17 G17 C12 D4 K3 R16 
MARK \t@C6
COM
Problem 109. Black to play.  

The marked white stone on the left is outnumbered. How should
Black attack it ? 
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B 1 C5
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Black should make a diagonal attachment with 1.
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  VAR
  B 1 F4
  COM
  Failure.

  If Black jumps to 1, ...
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  W 2 C9
  MARK \t@C12
  COM
  ... White plays the checking extension of 2, so Black's marked
  stone comes under attack.
  <=
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  ENDVAR
W 2 D6
MARK A@F4
COM
White will stand at 2, but instead of jumping to A, ...
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B 3 C9
COM
... Black will pincer with 3. The two white stones are now heavy
and under attack.
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W 4 E4
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If White attaches with 4, ...
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B 5 E3
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... after the exchange of Black 5 ...
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W 6 F4
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... for White 6, ...
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B 7 D5
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... Black 7 is the vital point.
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W 8 E6
COM
After White 8, ...
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B 9 D3
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... Black secures his stones in the corner with 9.
<=
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