EVENT
BOARDSIZE 19
SETUP W D15 D14 C14 C10 C8 C7 C6 C5 B4 R3 J7 L6 N5 O5 O4 P3 P4 Q4 R6 Q7 R8 S7 R12 Q11 P11 O10 O9 N11 N12 M11 L11 L12 Q16 O17 L17 
SETUP B D17 F17 C16 C15 B7 B6 B5 C4 C3 D5 E3 Q3 Q2 P2 O3 N2 N4 M4 K5 S8 R10 N9 N10 M12 L13 M14 N13 O11 O12 P12 O14 P14 P13 R14 S16 R17 
MARK \t@L17 \t@O17 \t@Q16
COM
Problem 91. Black to play.  

How should Black attack the three marked stones ? 
ENDCOM
B 1 L18
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Attaching with Black 1 in an interesting move.. Next ...
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  VAR
  B 1 J17
  COM
  Failure.

  Black 1 is the move many players would make, but ...
  ENDCOM
  W 2 K17
  COM
  ... White easily makes a living group with 2 ...
  ENDCOM
  B 3 J16
  W 4 Q17
  COM
  ... and 4.
  <=
  ENDCOM
  ENDVAR
  VAR
  B 1 P18
  COM
  Failure.

  If Black slides to 1, ...
  ENDCOM
  W 2 H17
  COM
  ... White would extend to 2, and again her stones are alive.
  <=
  ENDCOM
  ENDVAR
W 2 K18
COM
If White plays on the outside with 2, ...
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  VAR
  W 2 M18
  COM
  Variation.

  If White blocks on the inside with 2, ...
  ENDCOM
  B 3 K18
  COM
  ... Black will draw back to 3.
  ENDCOM
  W 4 M16
  COM
  After 4, Black continues to attack the white stones with 5, while
  building territory in the top left, ...
  ENDCOM
  B 5 J16
  W 6 Q17
  COM
  ... so White has to play 6 to secure her isolated stones. Again,
  Black ends in sente.
  <=
  ENDCOM
  ENDVAR
B 3 M17
W 4 M18
B 5 N18
W 6 L19
B 7 N17
MARK b@H17 A@J17 \t@Q16 \t@O17
COM
... Black will capture the two marked stones with the sequence
to 7. Black is now threatening to kill the white stones by attacking
at A, so White has to play B in gote to ensure that her stones
are alive.
<=
ENDCOM