EVENT
BOARDSIZE 19
SETUP W G16 C16 C13 C4 N4 R4 Q6 P6 O7 
SETUP B E17 F15 E3 P3 P5 O5 Q8 Q11 P17 R16 
MARK \t@Q11
COM
Problem 4. White to play.  

Black has just extended with the marked stone. How can White
take the initiative at the bottom ? 
ENDCOM
W 1 Q3
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Attaching with White 1 robs the black stones of their base and
gives White the territory in the lower right corner. Next ...
ENDCOM
  VAR
  W 1 M6
  COM
  Failure.

  Confining the three black stones with White 1 is a dubious move.
  ENDCOM
  B 2 R3
  COM
  Black attaches with 2 and ...
  ENDCOM
  W 3 S3
  B 4 R2
  MARK A@G3
  COM
  ... easily makes life in the corner after descending to 4. Even
  if White attacks the stone in the lower left corner at A, she
  can't expect a big profit. The sequence in the Correct Answer
  Diagram is superior to the one here.
  <=
  ENDCOM
  ENDVAR
B 2 N5
W 3 L4
B 4 M6
MARK 2@N5
COM
... Black has to run away with 2 and 4, but ...
ENDCOM
W 5 G3
MARK 3@L4
COM
... White jumps to 3 and extends to 5, mapping out territory
along the bottom and attacking the black stone in the lower left
corner. In addition, the black stones at the bottom right are
still without a base. With two vulnerable positions under attack,
Black is at a serious disadvantage.
<=
ENDCOM