EVENT
BOARDSIZE 19
SETUP W D15 D17 H17 H15 C10 R17 R16 R15 S14 R13 S12 
SETUP B K17 K15 Q17 Q16 Q15 R18 S13 R14 Q14 Q10 
MARK 1@R18 B@S15 A@S18
COM
Problem 101. White to play.  

After White 3 in the Correct Answer of Problem 98, Black 1 is
the vital point. If White blocks at A, Black will atari at B.
What should White do ? 
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W 1 T13
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Capturing with 1 leaves White with good aji.
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  VAR
  W 1 S16
  COM
  Failure.

  White could also respond with 1, ...
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  B 2 Q13
  COM
  ... but Black ataris with 2. Black is putting all his stones
  to good use.
  <=
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  ENDVAR
B 2 S17
W 3 S16
B 4 T16
MARK 2@S17
COM
Black gets to play forcing moves with 2 and 4, ...
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W 5 S15
COM
... but that cannot be helped.
<=
ENDCOM