(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PB[Black to play]AW[cn][dn][en][bo][eo][dp][dq][br][cr][dr]AB[co][do][cp][ep][bq][cq][eq][ar][er]C[This is the problem position.
Black to play.]
(;B[ds]C[If black tries to fill the liberties he fails
becuase he cannot play in the corner
without being self-atari.]
;W[bp]
;B[aq]
;W[bs]
;B[as]
;W[ap])
(;B[bs]C[Filling this liberty is not fast enough either.]
;W[bp]
;B[aq]
;W[ap]C[Filling this ]
;B[ds]
;W[as])
(;B[aq]C[Connecting is no good]
;W[ap]
;B[ds]
;W[bp]
;B[bs]
;W[as])
(;B[ap]C[Nor does this work.]
;W[bp]
;B[aq]
;W[ao])
(;B[bn]C[Cutting here first is the trick. This is the correct move.]
;W[bp]
;B[aq]
(;W[ap]C[This is now self-atari for white])
(;W[bm]C[White has to waste time capturing the cutting stone.]
;B[ds]
;W[an]
;B[bs]
;W[ap]
;B[cs]C[Black acaptures white.])))
