EVENT
BOARDSIZE 19
SETUP W D16 D14 C6 D4 Q5 S6 R7 Q7 P6 O6 O5 Q18 O17 M17 
SETUP B F3 K4 Q3 Q6 R6 R5 S5 P5 P4 O4 R9 Q14 Q16 R17 
MARK \t@O5 \t@O6 \t@P6 \t@Q7 \t@R7 \t@S6
COM
Problem 3. Black to play.  

White's marked stones in the lower right are vulnerable. How
should Black attack them ? 
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B 1 P8
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Peeping with Black 1 is severe. Next ...
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  VAR
  B 1 F5
  COM
  Failure.

  Locally, Black 1 is a strong move, but it only focuses on reinforcing
  Black's moyo at the bottom.
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  W 2 P8
  COM
  White secures his stones by making shape with 2, and Black's
  attacking chance vanishes.
  <=
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  ENDVAR
W 2 P7
COM
... White must connect with 2.
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B 3 O8
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Black 3 is a vital point which prevents White from making shape
in the center.
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W 4 M6
COM
After White jumps to 4, ...
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B 5 K6
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... Black attacks the whole white group with 5.
ENDCOM