(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[13]KM[0.00]
PB[Noir]AW[gi][hi][ii][ji][bj][cj][dj][ej][jj][kj][bk][fk][gk][lk][bl][el][kl][em][jm][km]AB[ij][ck][dk][ek][hk][jk][cl][fl][gl][il][jl][bm][cm][im]
;B[]
(;W[gm]C[The key : White will sacrifice  four stones]
(;B[hm]
;W[fm]
;B[hl]
;W[al]C[else:]
(;B[dl]
;W[am]
;B[dm]
;W[fm]C[double threat]
(;B[el]
;W[hj])
(;B[hj]
;W[el]))
(;B[hj]
;W[am]C[seki, but  not for ever...]))
(;B[hl]
;W[fm]
;B[hm]C[Same situation]))
(;W[hj]
(;B[fm]
(;W[hl]
;B[hm]
;W[ik]
;B[hl]
;W[kk]C[Ko:]
;B[ij]
;W[al]
;B[dl])
(;W[ik]
;B[hl]
;W[al]
;B[dl]C[Black lives without ko]))
(;B[ik]
;W[gm]
(;B[hl]
;W[fm]C[Black is dead])
(;B[hm]
;W[fm]))))
