EVENT
BOARDSIZE 19
SETUP W B16 C16 D17 E16 R14 R10 R4 P3 C12 C11 D11 
SETUP B G17 K17 O16 Q16 K3 D4 C15 D15 C13 D12 E12 
COM
Problem 174. Black to play.  

In this position, the first thing you should focus on is the
group of three white stones on the left side. How should Black
attack them ? 
ENDCOM
B 1 C7
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Black 1 is the ideal point to attack the white stones.
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  VAR
  B 1 C6
  COM
  Failure.

  Black 1 leaves room ...
  ENDCOM
  W 2 C8
  COM
  ... for a white extension to 2.
  <=
  ENDCOM
  ENDVAR
  VAR
  B 1 C8
  COM
  Failure.

  Black 1 would be too close to White's thick position above.
  <=
  ENDCOM
  ENDVAR
  VAR
  B 1 E11
  COM
  Failure.

  Black 1 ...
  ENDCOM
  W 2 E10
  B 3 F10
  COM
  ... and 3 are in the wrong direction.
  ENDCOM
  W 4 E9
  B 5 C7
  COM
  Black must now extend to 5, but ...
  ENDCOM
  W 6 B8
  COM
  ... White settles her stones with 6.
  <=
  ENDCOM
  ENDVAR
  VAR
  B 1 N3
  COM
  Failure.

  Black has to attack the white stones on the left. If he extends
  to 1 at the bottom right, ...
  ENDCOM
  W 2 C6
  COM
  ... White will approach to 2 and ...
  ENDCOM
  B 3 F4
  W 4 B4
  B 5 C3
  W 6 E11
  B 7 F12
  W 8 G10
  COM
  ... her stones on the left side will be settled.
  <=
  ENDCOM
  ENDVAR
W 2 E11
MARK 1@C7
COM
In response to Black 1, White must run away with 2 ...
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  VAR
  W 2 B13
  COM
  Variation.

  If White plays 2, ...
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  B 3 B15
  W 4 D13
  B 5 E13
  W 6 C14
  B 7 D14
  MARK B@E18 A@F15
  COM
  ... the sequence to Black 7 would follow. After this, confining
  White with Black A or sliding to Black B would be a severe attack
  on the white stones.
  <=
  ENDCOM
  ENDVAR
B 3 F12
W 4 G10
COM
... and 4.
ENDCOM
B 5 H11
COM
While Black is chasing White, he is going to be building a moyo
at the top and strengthening his stones in the lower left.
<=
ENDCOM