EVENT
BOARDSIZE 19
SETUP W C16 E16 K17 N17 R14 Q14 P10 R10 R17 S17 
SETUP B C10 P17 Q17 Q16 R15 S16 
MARK D@S18 C@Q15 B@S15 A@R16 4@Q17 2@S16 3@S17 1@R17
COM
Problem 135. White to play.  

The moves from White 1 to Black 4 have been played. White would
like to play A - Black B - White C, but Black would then play
a tesuji at D, capturing White's stones in the corner. How should
White play ? 
ENDCOM
W 1 S18
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

White 1 is the vital point.
ENDCOM
B 2 S14
COM
If Black defends his weakness by playing 2, ...
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  VAR
  B 2 Q18
  COM
  Failure.

  Black 2, trying to kill White, is a bad move.
  ENDCOM
  W 3 R16
  COM
  White plays 3 and ...
  ENDCOM
  B 4 S15
  W 5 Q15
  COM
  ... cuts with 5, winning the capturing race in the corner by
  one move.
  <=
  ENDCOM
  ENDVAR
W 3 Q18
B 4 P18
W 5 Q19
MARK 3@Q18
COM
... White lives in the corner with 3 and 5.
<=
ENDCOM