EVENT
BOARDSIZE 19
SETUP W L17 P16 R16 B16 C14 C11 
SETUP B C17 D16 F16 J17 
COM
Problem 111. Black to play.  

White's extension is one space narrower than in Problem 108.
Where should Black invade ? 
ENDCOM
B 1 N17
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Black 1 is the vital point. We will look at the variations in
the next few problems.
<=
ENDCOM
  VAR
  B 1 Q17
  MARK @@N17
  USER
  CORRECT ANSWER
  ENDUSER
  COM
  Correct Answer.

  Black could also peep at 1. However, Black @ in the Correct Answer
  is the usual move.
  <=
  ENDCOM
  ENDVAR
  VAR
  B 1 M17
  USER
  CORRECT ANSWER
  ENDUSER
  COM
  Correct Answer.

  Attaching at Black 1 is also possible.
  <=
  ENDCOM
  ENDVAR