EVENT
BOARDSIZE 19
SETUP W D16 D4 O17 
SETUP B Q4 Q10 Q16 M16 
MARK \t@M16 A@M17
COM
Problem 10. White to play.  

Instead of the usual low pincer at A, Black has pincered on the
fourth line with the marked stone. How should White respond ?
ENDCOM
W 1 O15
MARK A@O16
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Black is threatening to shut White out of the center with A.
Therefore, jumping to White 1 is essential.
ENDCOM
  VAR
  W 1 R17
  COM
  Failure.

  Invading with 1 may be possible in some positions, but here,
  with Black's sanren-sei formation in place, it is a bad move.
  ENDCOM
  B 2 R16
  W 3 Q17
  B 4 P16
  W 5 P17
  B 6 O16
  W 7 N17
  B 8 N16
  COM
  Up to 8, Black gets a thick wall without any defects. Compare
  this with the result when Black makes the low pincer, as in the
  Correct Answer of Problem 2.
  <=
  ENDCOM
  ENDVAR
B 2 Q14
COM
After Black 2, ...
ENDCOM
W 3 Q18
B 4 R17
W 5 M18
MARK 3@Q18
COM
... White settles her stones with 3 and 5.
<=
ENDCOM