EVENT
BOARDSIZE 19
SETUP W D16 K16 O17 D4 N5 Q5 
SETUP B Q16 Q14 Q9 K4 Q3 R4 
MARK 1@N5
COM
Problem 43. Black to play.  

White 1 is a good move because it is light and aims to make sabaki.
Black, however, must not play passively. Instead, he must pursue
White persistently. Where should he play ? 
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B 1 P4
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Before anything else, Black must play 1, ...
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  VAR
  B 1 R5
  COM
  Failure for Black.

  If Black crawls at 1, ...
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  W 2 N3
  MARK \t@K4
  COM
  ... White will jump into the bottom with 2, separating the marked
  stone from its allies on the right. This stone could come under
  attack later on.
  <=
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  ENDVAR
W 2 O6
B 3 N3
COM
... then take territory at the bottom with 3.
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W 4 O9
COM
After White caps at 4, this skirmish will come to a pause, but
Black still has attacking chances.
<=
ENDCOM