EVENT
BOARDSIZE 19
SETUP W B16 C14 C11 J17 M17 R14 R11 
SETUP B C17 D16 F17 O17 Q16 S16 
COM
Problem 149. White to play.  

Here is another tight black formation. Can White invade Black's
corner and live ? 
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W 1 R17
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

The moves from White 1 ...
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  VAR
  W 1 S15
  COM
  Alternative.

  Since White is unable to invade Black's corner, she should make
  this area as small as possible ...
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  B 2 R17
  W 3 O18
  B 4 P18
  W 5 O16
  MARK 1@S15 3@O18
  COM
  ... by playing the forcing moves of 1, 3, and 5.
  <=
  ENDCOM
  B 6 P17
  ENDVAR
B 2 R16
W 3 P18
B 4 O18
W 5 P17
B 6 P16
W 7 S17
COM
... to 7 are all good, but Black is too strong here and ...
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B 8 Q17
W 9 Q18
B 10 S18
COM
... White has no answer to Black 10.
<=
ENDCOM