EVENT
BOARDSIZE 19
SETUP W L17 M16 P16 R16 P17 B16 C14 C11 
SETUP B C17 D16 F16 J17 N17 Q17 
MARK 1@Q17 2@P17
COM
Problem 117. Black to play.  

In answer to Black 1, White blocks on the other side with 2.
How should Black respond ? 
ENDCOM
B 1 Q16
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Black makes life in the corner ...
ENDCOM
W 2 Q15
B 3 R17
W 4 R15
MARK 3@R17
  VAR
  W 4 P15
  COM
  Variation.

  When Black plays 3, White could connect at 4, ...
  ENDCOM
  B 5 S15
  COM
  ... but Black 5 becomes a tesuji.
  <=
  ENDCOM
    VAR
    B 5 P18
    COM
    Black could also play 5 here first, ...
    ENDCOM
    W 6 O18
    B 7 Q18
    W 8 O17
    B 9 S15
    COM
    ... then come back and play 9.
    <=
    ENDCOM
    ENDVAR
  ENDVAR
B 5 P18
W 6 O18
B 7 Q18
W 8 O17
B 9 S16
W 10 S15
B 11 S17
MARK A@P15
COM
... with the moves to 11. White must now defend against the cut
at A.
<=
ENDCOM