EVENT
BOARDSIZE 19
SETUP W E17 E16 R3 Q3 P4 L3 C4 D4 D6 E4 F4 E3 G3 H3 B12 C11 C13 D13 E14 F14 D11 
SETUP B D17 C16 J17 Q16 Q7 R4 S5 S3 F3 G4 F5 F2 E2 D2 C3 D14 C14 B14 B13 E13 E12 G12 
MARK A@E13 B@F14 C@E12 D@D11 E@G12
COM
Problem 100. White to play.  

Black plays the sequence to E, isolating the white stones at
the top. But Black's stones in the center are also weak. What
should White do ? 

[You will find a supplement to this Problem Diagram as "Problem 144"]
ENDCOM
W 1 J15
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

White should attack the black stone at the top by capping with
1.
ENDCOM
B 2 L16
COM
If Black responds with 2, 
ENDCOM
  VAR
  B 2 J12
  MARK 1@J15
  COM
  Variation.

  If Black answers the cap of White 1 by jumping to 2, ...
  ENDCOM
  W 3 K17
  COM
  ... White will attack the top ...
  ENDCOM
  B 4 K18
  W 5 K16
  B 6 L18
  W 7 M17
  B 8 M18
  W 9 N17
  B 10 N18
  W 11 H17
  B 12 H18
  W 13 J16
  B 14 J18
  W 15 O17
  COM
  ... with the sequence to 15.
  ENDCOM
  B 16 P18
  COM
  After Black defends the corner with 16, ...
  ENDCOM
  W 17 H11
  B 18 H12
  W 19 F10
  B 20 L12
  W 21 K10
  COM
  ... White maps out a moyo in the lower left with the sequence
  to 21.
  <=
  ENDCOM
  ENDVAR
W 3 J12
COM
... White goes on the offensive against the three black stones
in the center with 3 ...
ENDCOM
B 4 F10
W 5 J9
COM
... and 5. Black is in trouble.
ENDCOM
B 6 D9
MARK \t@J9
COM
After White plays the marked stone, Black might try to attack
the white stones in the upper left by invading with 6.
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  VAR
  B 6 H13
  COM
  Variation.

  Since White is thin in the center, Black can escape with 6 ...
  ENDCOM
  W 7 L15
  B 8 J13
  MARK 5@L15
  COM
  ... and 8, but Blacks stones become at the top become  vulnerable
  after White 5. Next ...
  ENDCOM
  W 9 K16
  COM
  ... White plays 9.
  ENDCOM
  B 10 H15
  COM
  If Black tries to capture the white stones in the top left by
  attaching with 10, 
  ENDCOM
  W 11 H16
  B 12 J16
  W 13 H14
  B 14 G15
  W 15 G14
  B 16 J14
  W 17 K15
  B 18 G16
  W 19 K17
  B 20 G17
  W 21 J18
  B 22 H17
  W 23 F18
  B 24 G18
  W 25 G19
  B 26 H19
  W 27 F19
  B 28 H18
  W 29 K18
  COM
  ... he will find himself caught up in a capturing race that he
  has no hope of winning. This would be a disaster for Black.
  <=
  ENDCOM
  ENDVAR
W 7 C9
B 8 C8
W 9 D8
B 10 C10
W 11 B9
B 12 E8
W 13 D7
B 14 D10
W 15 B10
COM
However, White easily links up with the sequence to 15.
ENDCOM
B 16 F8
W 17 E10
B 18 E9
W 19 E11
B 20 F11
W 21 G9
COM
After peeping at 21, ...
ENDCOM
B 22 F9
W 23 H13
COM
... White makes a reinforcing move with 23 and the black stones
are trapped within White's sphere of influence.
<=
ENDCOM