(;AB[aq]AB[br]AB[cq]AB[dq]AB[dr]AB[cr]AB[ep]AB[fp]AB[gq]AB[gr]AW[bq]AW[bp]AW[cp]AW[dp]AW[eq]AW[er]AW[fr]AW[ds]AP[goproblems]
(;W[bs]
(;B[as]
(;W[ar]C[Ko, White takes first. If Black plays a ko threat and retakes then White can play A4; if Black next takes C1 White starts the ko anew. So A4 is like a free internal ko threat.RIGHT])
(;W[ap];B[cs]
(;W[ar];B[es]
(;W[fs];B[gs];W[ds];B[aq]C[Black lives with double ko.])
(;W[bs]C[Direct ko, White takes first. But now White has no internal threats. White F1 just lets Black live with double ko.])
(;W[aq];B[fs]))
(;W[es];B[fq])
(;W[fs];B[gs];W[ar];B[es]C[Black is alive with double ko.]))
(;W[es];B[cs];W[ap];B[fq]))
(;B[ar]
(;W[ap]C[RIGHT])
(;W[cs]C[RIGHT])
(;W[es]C[RIGHT])))
(;W[ar];B[as]
(;W[ap];B[fq])
(;W[cs];B[fs]
(;W[ap];B[fq])
(;W[es];B[gs];W[ap];B[fq])))
(;W[ap];B[fs]
(;W[ar];B[fq])
(;W[es];B[fq];W[gs];B[cs])
(;W[cs];B[fq])
(;W[bs];B[fq]))
(;W[cs];B[bs]
(;W[es];B[fq])
(;W[ar];B[es])
(;W[fs];B[gs])
(;W[ap];B[fs])))
