(;AB[br]AB[bq]AB[co]AB[do]AB[eo]AB[fo]AB[go]AB[ho]AB[hp]AB[hr]AB[jr]AB[fr]AW[cs]AW[cr]AW[dq]AW[dp]AW[fp]AW[gp]AW[gq]AW[gr]AW[gs]C[Black to kill (no ko)]AB[hq]AB[bs]AP[goproblems]
(;B[dr]
(;W[cq]C[CHOICE]
(;B[eq]
(;W[ep]C[CHOICE]
(;B[es]C[Black built an eye and white dies. If e2 was filled, - that would have been a seki.CHOICERIGHT])
(;B[er];W[es]C[seki]
(;B[cp];W[fq]C[as i said, - seki])
(;B[hs];W[fq])))
(;W[es];B[ep];W[er];B[fq]C[RIGHT]))
(;B[er];W[es]
(;B[ep];W[eq]C[seki])
(;B[fs];W[eq]C[])
(;B[ds];W[eq])
(;B[eq];W[ep]))
(;B[es];W[eq]C[]
(;B[er];W[ep]C[seki])
(;B[ep];W[er])
(;B[hs];W[er])
(;B[cp];W[er]))
(;B[ep];W[eq]C[]
(;B[er];W[es]C[seki])
(;B[cp];W[er])
(;B[hs];W[er])))
(;W[er];B[eq]
(;W[es]C[];B[ep];W[fq];B[cq]C[RIGHT])
(;W[ds];B[ep];W[fq];B[fs];W[es];B[cq]C[RIGHT])
(;W[ep];B[es]C[RIGHT]))
(;W[ep];B[es]
(;W[cq]C[];B[eq]C[RIGHT])
(;W[eq];B[cq]C[RIGHT])
(;W[fq];B[er]C[RIGHT]))
(;W[es];B[cq]
(;W[er];B[ds]C[RIGHT])
(;W[ds];B[er]C[RIGHT])
(;W[ep];B[er]C[RIGHT])))
(;B[eq];W[ep]
(;B[dr];W[es]C[]
(;B[cq];W[er]
(;B[ds];W[fq])
(;B[fq];W[ds]))
(;B[er];W[cq]C[seki]))
(;B[er];W[cq]C[]
(;B[fs];W[dr]C[]LB[es:ko]
(;B[es]C[seki])
(;B[ds];W[fq])
(;B[cp]C[white can either start ko with e1 or wait for black to do it (I believe, it is called 'man en ko' - 'a 10000-year ko' in Japan)])
(;B[hs]C[NOTTHIS]))
(;B[es]C[seki])
(;B[dr]))
(;B[es];W[dr]C[];B[er]C[seki]))
(;B[er];W[es]C[]
(;B[dr];W[cq])
(;B[ep];W[eq]
(;B[cq];W[dr])
(;B[dr];W[cq]C[seki]
(;B[hs];W[fq])
(;B[fq];W[ds])
(;B[cp];W[fq]))
(;B[fs];W[dr]C[];B[ds];W[fq]))
(;B[fs];W[dr]C[]
(;B[ep];W[eq])
(;B[ds];W[ep]
(;B[es]C[seki])
(;B[cp];W[es]C[ko])
(;B[cq]C[ko];W[es])
(;B[hs]C[ko];W[es])))
(;B[cq];W[dr]
(;B[fs];W[fq];B[ds];W[eq])
(;B[ep];W[eq])))
(;B[es];W[er]C[]
(;B[eq];W[ds]C[ko is not a solution]
(;B[ep];W[fq]C[ko])
(;B[dr]C[koNOTTHIS])
(;B[cq];W[fs])
(;B[fq];W[ep]C[ko]))
(;B[fs];W[ds])
(;B[cq];W[fs])
(;B[ep];W[eq]
(;B[fs];W[ds])
(;B[cq];W[fs]))
(;B[fq];W[eq]))
(;B[ep];W[eq]
(;B[er];W[es])
(;B[es];W[er])
(;B[dr];W[er]))
(;B[cq];W[er]
(;B[es])
(;B[ep];W[eq])
(;B[ds];W[dr])
(;B[fs];W[es]
(;B[dr];W[ep]
(;B[ds];W[fq])
(;B[fq];W[ds]))
(;B[ep];W[eq])
(;B[eq];W[ep]))))