Black to get any ko to kill white. See also problem 6327
(;GM[1]FF[4]CA[UTF-8]AP[CGoban:2]ST[2]
RU[Japanese]SZ[19]KM[0.50]
PW[White]PB[Black]AW[pl][dm][jm][mm][pm][dn][en][gn][hn][in][mn][co][do][eo][fo][ho][io][lo][mo][oo][bp][dp][fp][ip][jp][dq][eq][mq][nq][cr][er][fr][gr][lr][mr]AB[ci][qk][dl][ql][cm][em][fm][gm][qm][bn][cn][fn][ln][pn][bo][go][jo][ko][po][cp][gp][kp][lp][pp][cq][fq][gq][hq][iq][jq][lq][br][dr][hr][kr][pr][bs][ds]PL[B]
(;B[cs]CR[cs]
;W[bq]CR[bq]
(;B[cr]CR[cr]
;W[es]CR[es]
(;B[ap]CR[ap]
;W[gs]CR[gs]C[White lives])
(;B[gs]CR[gs]
;W[ar]CR[ar]))
(;B[ar]CR[ar]
;W[cr]CR[cr]
(;B[cq]CR[cq]
;W[aq]CR[aq]
(;B[ao]CR[ao]
;W[es]CR[es]
(;B[cr]CR[cr]
;W[cp]CR[cp])
(;B[hs]CR[hs]
;W[gs]CR[gs])
(;B[gs]CR[gs]
;W[cp]CR[cp]
(;B[hs]CR[hs]
;W[cr]CR[cr]C[RIGHT Notes that this is a three step ko for black. Black stands to lose a lot in the corner, and can't really expect to win this ko.])
(;B[ap]CR[ap]
;W[cr]CR[cr]C[RIGHT Notes that this is a three step ko for black. Black stands to lose a lot in the corner, and can't really expect to win this ko.]))
(;B[ap]CR[ap]
;W[gs]CR[gs]C[White lives]))
(;B[cr]CR[cr]
;W[cp]CR[cp])
(;B[es]CR[es]
;W[ao]CR[ao]
(;B[an]CR[an]
;W[cp]CR[cp]
;B[ap]CR[ap]
;W[cr]CR[cr]C[White lives in double ko.])
(;B[fs]CR[fs]
;W[gs]CR[gs]
(;B[hs]CR[hs]
;W[cp]CR[cp]
;B[an]CR[an]
;W[cr]CR[cr]C[White lives in double ko])
(;B[an]CR[an]
;W[cp]CR[cp]
(;B[ap]CR[ap]
;W[cr]CR[cr]C[White lives in double ko.])
(;B[hs]CR[hs]
;W[cr]CR[cr]C[White lives in double ko.])))
(;B[gs]CR[gs]
;W[fs]CR[fs]
;B[hs]CR[hs]
;W[cp]CR[cp]
;B[an]CR[an]
;W[cr]CR[cr]C[White lives in double ko.]))
(;B[gs]CR[gs]
;W[ao]CR[ao]
;B[an]CR[an]
;W[cp]CR[cp]
(;B[ap]CR[ap]
;W[cr]CR[cr]C[White lives in double ko])
(;B[es]CR[es]
;W[fs]CR[fs]
;B[hs]CR[hs]
;W[cr]CR[cr]C[White lives in double ko.])
(;B[fs]CR[fs]
;W[es]CR[es]
;B[hs]CR[hs]
;W[cr]CR[cr]C[White lives in double ko.])))
(;B[ap]CR[ap]
;W[cq]CR[cq])
(;B[aq]CR[aq]
;W[cq]CR[cq]))
(;B[aq]CR[aq]
;W[cr]CR[cr]
(;B[cq]CR[cq]
;W[ar]CR[ar])
(;B[ap]CR[ap]
;W[cq]CR[cq])
(;B[ar]CR[ar]
;W[cq]CR[cq]))
(;B[gs]CR[gs]
;W[cr]CR[cr]
;B[cq]CR[cq]
;W[ar]CR[ar])
(;B[es]CR[es]
;W[cr]CR[cr]
;B[cq]CR[cq]
;W[ar]CR[ar]))
(;B[bq]CR[bq]
;W[es]CR[es]
;B[cs]CR[cs]
;W[gs]CR[gs]C[White lives])
(;B[gs]CR[gs]
;W[bq]CR[bq]
(;B[ap]CR[ap]
;W[cq]CR[cq])
(;B[aq]CR[aq]
;W[cq]CR[cq])
(;B[ar]CR[ar]
;W[cq]CR[cq])
(;B[cq]CR[cq]
;W[ar]CR[ar])))