EVENT
BOARDSIZE 19
SETUP W D17 G17 J16 D11 D10 F11 E9 G9 J9 Q4 
SETUP B H15 F15 C15 D9 D8 E8 D4 G7 Q16 
MARK \t@J9 C@D3 A@J7 B@K4
COM
Problem 115. Black to play.  

White runs away with the marked stone. Should Black continue attacking
with A, map out a moyo with B or secure territory with C ? 
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B 1 D3
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

The first thing Black must do is to defend his territory on the
left by enclosing with 1.
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  VAR
  B 1 J7
  COM
  Failure.

  Black 1 is not a very forceful attack.
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  W 2 C3
  COM
  White will snatch the corner territory from Black with the 3-3
  point invasion of 2.
  <=
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  ENDVAR
  VAR
  B 1 K4
  COM
  Failure.

  Against Black 1 here, ...
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  W 2 C3
  COM
  ... White will also invade at 2.
  <=
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  ENDVAR
W 2 O17
COM
If White next approaches with 2, ...
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  VAR
  W 2 K3
  COM
  If White 2 here, Black will play at the top.
  <=
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  ENDVAR
B 3 K14
COM
... Black exchanges 3 ...
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W 4 L16
COM
... for 4, ...
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B 5 K3
COM
... then maps out a moyo with 5.
<=
ENDCOM