EVENT
BOARDSIZE 19
SETUP W C17 D16 C15 D15 D14 F17 L16 P13 P11 R11 Q6 R6 R5 R4 Q4 R3 Q2 R1 S2 D3 D5 C9 C13 
SETUP B H17 J15 P17 R16 R13 Q8 O8 S7 Q3 P3 P2 P4 P5 Q5 P6 J4 C11 B16 C14 D13 E13 E14 
MARK \t@L16
COM
Problem 56. Black to play.  

How should Black attack the marked white stone at the top ? 
ENDCOM
B 1 O14
MARK \t@L16
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Black 1 aims at both the marked stone and the three white stones
on the right side.
ENDCOM
  VAR
  B 1 L14
  COM
  Failure.

  If Black immediately caps with 1, ...
  ENDCOM
  W 2 O16
  COM
  ... White makes a shoulder hit at the vital point of 2.
  ENDCOM
  B 3 P16
  W 4 O15
  COM
  After 4, White's stones form a cohesive and resilient group,
  having a lot of room to maneuver. It will be hard for Black to
  find an effective attack against them.
  <=
  ENDCOM
  ENDVAR
  VAR
  B 1 N16
  COM
  Failure.

  Black 1 is completely unconvincing.
  ENDCOM
  W 2 L14
  COM
  White jumps down into the center with 2, and Black doesn't have
  a good follow-up.
  <=
  ENDCOM
  ENDVAR
W 2 O13
COM
If White defends with 2, ...
ENDCOM
  VAR
  W 2 L14
  MARK 1@O14
  COM
  Variation.

  In answer to Black 1, White might escape into the center with
  2, but ...
  ENDCOM
  B 3 N12
  MARK \t@R11 \t@P11 \t@P13
  COM
  ... the three marked stones are in trouble after Black 3.
  <=
  ENDCOM
  ENDVAR
B 3 L14
MARK \t@L16
COM
... Black caps with 3 and the marked stone is trapped.
<=
ENDCOM