EVENT
BOARDSIZE 19
SETUP W F17 F16 K17 R16 S16 S15 
SETUP B D16 E17 D14 N17 Q16 R17 S17 R15 R10 
MARK 2@S16 3@S17 1@R17 \t@S15
COM
Problem 142. White to play.  

Black takes the corner with 1 and 3. What should White do ? 
ENDCOM
W 1 Q15
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

White should cut with 1, ...
ENDCOM
B 2 R14
W 3 Q17
COM
... then atari with 3.
ENDCOM
B 4 P16
W 5 S14
B 6 P17
COM
After Black takes the corner with 6, ...
ENDCOM
  VAR
  B 6 R13
  COM
  Variation.

  Black extends to 6, aiming to get thickness in the center.
  ENDCOM
  W 7 Q18
  COM
  However, White takes the corner with 7.
  <=
  ENDCOM
  ENDVAR
W 7 R13
B 8 Q14
W 9 P13
MARK 7@R13
COM
... White makes sabaki with 7 and 9.
<=
ENDCOM