EVENT
BOARDSIZE 19
SETUP W M17 N16 Q17 R15 C14 D14 C11 
SETUP B C15 D16 F16 K17 O17 
MARK \t@O17 1@N16
COM
Problem 87. Black to play.  

What should Black do when White tries to enclosure the marked
stone with the diagonal move of 1 ? 
ENDCOM
B 1 P16
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Black should answer with 1.
ENDCOM
  VAR
  B 1 O16
  COM
  Failure.

  Black 1 is bad.
  ENDCOM
  W 2 O15
  B 3 P15
    VAR
    B 3 Q16
    COM
    If Black plays 3 here, ...
    ENDCOM
    W 4 R16
    B 5 P15
    W 6 Q15
    B 7 P16
    W 8 P14
    COM
    ... the moves to White 8 follow and Black's stones are almost
    dead.
    <=
    ENDCOM
    ENDVAR
  W 4 P16
  MARK 2@O15
  COM
  White confines the black stones to the top with 2 and 4.
  <=
  ENDCOM
  ENDVAR
W 2 O15
COM
If White continues with 2, ...
ENDCOM
B 3 Q16
W 4 R16
B 5 R17
MARK 3@Q16
COM
... Black pushes through and cuts with 3 and 5, ...
ENDCOM
W 6 Q18
B 7 P14
MARK 5@R17 A@P15
COM
... then jumps to 7. White cannot push through at A because of
the aji of 5.
<=
ENDCOM