EVENT
BOARDSIZE 19
SETUP W E18 D17 C16 D14 G16 Q18 P18 O17 L17 P14 R14 S14 Q13 Q12 R11 R6 S4 B3 D3 D4 E4 E2 C6 C7 D8 D9 F9 H9 K9 
SETUP B E17 G17 H16 G15 F15 R18 R17 L15 O14 P13 Q14 Q15 Q16 R15 Q4 O3 E3 G4 F4 E5 D5 C5 B5 D11 F11 D7 E7 H7 K7 
MARK \t@S4
COM
Problem 126. Black to play.  

White slides into the corner with the marked stone. What should
Black do ? 
ENDCOM
B 1 P7
MARK A@R7
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Black jumps all the way out with 1, aiming at A.
ENDCOM
  VAR
  B 1 Q6
  COM
  Failure.

  Black 1 ...
  ENDCOM
  W 2 Q7
  B 3 P6
  COM
  ... and 3 are not good because ...
  ENDCOM
  W 4 Q8
  B 5 G10
  W 6 G9
  B 7 J10
  W 8 J9
  B 9 O8
  COM
  ... Black ends in gote with 9.
  ENDCOM
  W 10 L11
  MARK A@C11
  COM
  White can now play 10. In this variation, White still has the
  option to attach at A.
  <=
  ENDCOM
  ENDVAR
W 2 Q8
COM
White defends with 2 and ...
ENDCOM
B 3 P8
COM
... Black pushes with 3, ...
ENDCOM
W 4 Q9
COM
... forcing White to extend to 4.
ENDCOM
B 5 G10
W 6 G9
B 7 J10
W 8 J9
B 9 L11
COM
Black now attacks with the sequence to 9. The white stones on
the left are in a pinch. Next ...
ENDCOM
  VAR
  B 9 C10
  COM
  Failure.

  Attacking White's eye shape with Black 9 is not good.
  ENDCOM
  W 10 L11
  COM
  White can take the vital point of 2 and Black won't be able to
  make much territory at the top.
  <=
  ENDCOM
  ENDVAR
W 10 C11
COM
White has to make eye shape for her stones. She does this by
playing at 10 and ...
ENDCOM
B 11 C12
W 12 B11
B 13 B12
W 14 D10
B 15 D12
W 16 B9
MARK A@F18
COM
... playing the sequence to 16. Black ends in sente, and the
moyo and territory he has built below and above are enough to
win. Next, Black can attack the white stones in the upper left
corner by playing A in sente. If Black becomes thick around here,
it could affect the white stones in the upper right.
<=
ENDCOM