EVENT
BOARDSIZE 19
SETUP W E16 F16 F17 Q4 D4 F3 
SETUP B C16 D17 E17 R16 B4 C6 
MARK A@D15 B@C14 C@D14
COM
Problem 113. Black to play.  

In the upper left corner, all the moves from A to C are josekis,
but, in relation to Black's other stones, only one of these choices
is correct. Which one is it ? 
ENDCOM
B 1 D15
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

The diagonal move of Black 1 is best.
ENDCOM
  VAR
  B 1 C14
  COM
  Failure.

  If Black 1, all his stones on the left are low.
  ENDCOM
  W 2 K17
    VAR
    W 2 C3
    COM
    If White 2 next, ...
    ENDCOM
    B 3 D8
    MARK A@C10
    COM
    ... Black plays 3 to maintain a high-low balance, but then an
    invasion at A remains.
    <=
    ENDCOM
    ENDVAR
  B 3 P17
  COM
  <=
  ENDCOM
  ENDVAR
  VAR
  B 1 D14
  COM
  Failure.

  If Black 1 here, ...
  ENDCOM
  W 2 C12
  COM
  ... White 2 is a severe attack.
  <=
  ENDCOM
  ENDVAR
W 2 K17
B 3 P17
W 4 C3
B 5 C9
W 6 R7
B 7 Q10
W 8 N17
B 9 L3
MARK 5@C9 1@D15
COM
The sequence to 9 is one possible continuation. Black 5 and the
stone at 1 make an ideal high-low balance on the left side.
<=
ENDCOM