EVENT
BOARDSIZE 19
SETUP W C17 C16 D15 C11 C8 D3 R10 
SETUP B C18 D17 E18 F16 Q4 Q16 C5 
MARK \t@C5
COM
Problem 108. Black to play.  

White is strong on the upper left side, so what should Black
do about his marked stone in the lower left ? 
ENDCOM
B 1 G3
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Black should make a counterpincer with 1.
ENDCOM
  VAR
  B 1 F5
  MARK \t@C8
  COM
  Failure.

  Against the two-space pincer of the marked white stone, Black
  1 is the usual move, but White is strong on the left side, ...
  ENDCOM
  W 2 G3
  COM
  ... so White will extend to 2, making territory while keeping
  up the pressure on Black.
  <=
  ENDCOM
  ENDVAR
W 2 E4
COM
When White makes the diagonal move of 2, ...
ENDCOM
B 3 K3
MARK \t@C5
COM
... Black can extend to 3, taking up a position at the bottom.
By treating the marked stone lightly, Black puts the burden of
what to do about this stone on White.
ENDCOM
W 4 D6
COM
If White next plays 4, ...
ENDCOM
B 5 R7
COM
... Black will extend to 5.
<=
ENDCOM