(;AB[cr]AB[dr]AB[cs]AW[ds]AW[es]AW[er]AW[eq]AW[dq]AW[dp]AW[bq]AB[bo]AB[bn]AB[do]AB[en]AB[ep]AB[fo]AB[fp]AB[gq]AB[gr]C[Black to kill]AP[goproblems]
(;B[br]
(;W[bs]C[]
(;B[aq]
(;W[cq]C[CHOICE]
(;B[ar];W[ap];B[bp];W[as]C[];B[cr]C[RIGHT]LB[aq:1]LB[br:2])
(;B[ap];W[ar])
(;B[as];W[ap];B[bp];W[ar]C[ko]))
(;W[ap];B[cq]C[RIGHT])
(;W[bp];B[ap]C[RIGHT]))
(;B[as];W[bp])
(;B[bp];W[cq])
(;B[cq];W[cp])
(;B[ar];W[bp]))
(;W[ar];B[bs];W[bp];B[ap]C[RIGHT])
(;W[cq];B[bs]C[];W[bp];B[ap]C[RIGHT]))
(;B[ar];W[aq]
(;B[cq];W[cp])
(;B[br];W[cq]))
(;B[cq];W[cp]
(;B[br];W[bs]
(;B[as];W[bp])
(;B[ar];W[aq]))
(;B[bp];W[br])
(;B[bs];W[br]))
(;B[cp];W[cq]
(;B[br];W[bs])
(;B[ar];W[aq]))
(;B[aq];W[ar]
(;B[br];W[bp]
(;B[bs];W[ap])
(;B[as];W[ap]C[4-step ko]))
(;B[ap];W[br];B[cp];W[cq])
(;B[cq];W[cp]))
(;B[bp];W[cq]
(;B[ar];W[aq])
(;B[br];W[bs])
(;B[aq];W[ar];B[bs];W[br]))
(;B[bs];W[br]))