EVENT
BOARDSIZE 19
SETUP W D5 C4 D3 D2 Q9 P6 Q6 Q5 Q4 P3 R3 R2 R15 Q15 Q13 P13 Q17 F17 J17 
SETUP B C17 D16 D14 C10 C7 E3 E4 G4 L3 S3 R4 R5 Q7 R8 R9 Q12 R13 R14 
COM
Problem 161. Black to play.  

In this game, White has built up a moyo at the top. How should
Black erase it ? 
ENDCOM
B 1 K16
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

When you look at the thickness on the right, a light erasing
move is what comes in your mind. The shoulder hit of Black 1
is the best move. If you play any deeper, your stone will meet
with a severe counterattack, so you cannot expect to reduce White's
territory any more than this.
ENDCOM
  VAR
  B 1 K15
  COM
  Failure.

  A light erasing move such as Black 1 is inadequate.
  ENDCOM
  W 2 L16
  COM
  White is satisfied with the territory she gets after playing 2.
  <=
  ENDCOM
  ENDVAR
  VAR
  B 1 L17
  COM
  Failure.

  If you think of a deep invasion, Black 1 is the move, but ...
  ENDCOM
  W 2 K16
  MARK A@K15
  COM
  ... after White 2 or A, Black will come under a severe attack.
  Black will have to put all his energy into making life on the
  right.
  <=
  ENDCOM
  ENDVAR
W 2 K17
COM
White answers with 2, ...
ENDCOM
B 3 L16
W 4 J16
B 5 K14
W 6 J15
B 7 M13
COM
... and the joseki to Black 7 follows.
<=
ENDCOM