(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PB[Black to play]AW[bq][cq][br][er][fr]AB[ap][bp][cp][dp][fp][eq][gq][gr]C[This is the problem position. Black to play.]
;B[dr]
;W[dq]
;B[ds]
(;W[cs]C[This move is not correct for white.]
;B[bs]
;W[as]
;B[aq]
(;W[ar]
;B[fq]C[It's a double whamy and white can't capture
the two cutting stones because of self-atari.])
(;W[cr]
;B[ar]C[This is only one eye.]))
(;W[aq]C[This is white's strongest move.]
;B[bs]
;W[as]C[It's a ko where black takes first.]
;B[ar]
;W[jp]C[ko threat]
;B[jq]C[ko threat answer]
;W[as]C[retakes ko.]
;B[fq]C[But black can always give up the ko and
be happy to capture two of the stones.]
;W[cs]
;B[fs]))
