EVENT
BOARDSIZE 19
SETUP W K17 Q17 Q15 S14 
SETUP B D17 C14 H17 R13 R10 
COM
Problem 126. Black to play.  

This time the white enclosure is facing the other direction.
Where should Black invade ? 
ENDCOM
B 1 M17
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Invading at 1 is the vital point.
ENDCOM
W 2 L16
COM
White 2 is the standard response.
ENDCOM
  VAR
  W 2 O17
  COM
  Variation.

  If White defends from the other side with 2, ...
  ENDCOM
  B 3 L16
  COM
  ... Black attacks the lone white stone with 3.
  <=
  ENDCOM
  ENDVAR
B 3 P17
COM
Next, Black attaches at 3, and, ...
ENDCOM
  VAR
  B 3 N15
  MARK @@P17
  COM
  Variation.

  Instead of @, playing directly at 3 is also possible.
  <=
  ENDCOM
  ENDVAR
W 4 P16
B 5 O17
COM
... after 5, ...
ENDCOM
W 6 Q18
B 7 N15
COM
... jumps to 7.
<=
ENDCOM