EVENT
BOARDSIZE 19
SETUP W C16 E16 C12 H17 R17 P18 Q14 R14 R11 
SETUP B C10 K17 O16 Q16 R15 S16 P17 
MARK 1@P17
COM
Problem 140.White to play.  

How does White respond to Black 1 ? 
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W 1 S17
MARK A@R16
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

White 1 aims at A, ...
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B 2 S14
COM
... so Black must defend with 2.
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  VAR
  B 2 Q18
  COM
  Failure.

  Black 2 is unreasonable.
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  W 3 R16
  B 4 S15
  W 5 Q15
  MARK 3@R16
  COM
  White pushes through with 3 and 5, winning three black stones
  in a capturing race.
  <=
  ENDCOM
  ENDVAR
W 3 O18
COM
Next White extends to 3, ending the sequence in good shape.
<=
ENDCOM