(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PB[Black to play]AW[or][pr][qr][rr][sr]AB[ro][kq][mq][nq][oq][pq][qq][rq][lr]C[Black to play and kill]
(;B[nr]
;W[os]C[If Black just plays on the end, the White group gets
a live shape.])
(;B[os]C[This play sometimes works as if White blocks to its right there is not enough room for two eyes.]
(;W[nr]C[However this move lives.]
;B[ns]
;W[mr]
;B[ms]
;W[ps]
(;B[ls]
;W[rs])
(;B[rs]
;W[ls]
;B[ms]
;W[ns]))
(;W[ps]
;B[rs]
;W[nr]
;B[ns]
;W[mr]
;B[ms]
;W[ls]
;B[ms]
;W[ns]C[As does this sequence.]))
(;B[rs]C[The correct play in this classic problem is the point where White needs to play for two eyes]
(;W[qs]C[This answer is only one eye.]
;B[os]
;W[nr]
;B[ns]
;W[mr]
;B[ms])
(;W[nr]
(;B[qs]
;W[ns]
;B[ps]C[This way is seki.])
(;B[ns]C[Hoever Black can kill again with this.]
(;W[os]
;B[qs]
;W[ms]
;B[mr])
(;W[qs]
;B[os]
(;W[ms]
;B[mr])
(;W[mr]
;B[ms]))))))
