(;AB[cq]AB[dq]AB[eq]AB[dr]AB[es]AB[fs]AB[fr]AW[fq]AW[gq]AW[gr]AW[gs]AB[fp]AB[gp]AB[hp]AB[ip]AB[ir]AW[ep]AW[dp]AW[cp]AW[bp]AW[br]AW[cs]C[Can black live here? It seems impossible ...]AW[bn]AP[goproblems]
(;B[bq]
(;W[ds]C[CHOICE]
(;B[ar]
(;W[er]C[CHOICE]
(;B[bs]C[yes, ko is the best black can do here.RIGHT])
(;B[es]
(;W[bs];B[fr];W[fs];B[er];W[ap];B[aq]C[RIGHT])
(;W[fs]C[CHOICE];B[bs]C[koRIGHT]))
(;B[fs];W[cr])
(;B[fr]
(;W[bs];B[es])
(;W[fs]C[CHOICE])))
(;W[bs];B[er];W[ap];B[aq]C[obviously, white group dies firstRIGHT]TR[gs]TR[gr]TR[gq]TR[fq]))
(;B[cr];W[er])
(;B[bs];W[as])
(;B[aq];W[er])
(;B[er];W[aq]))
(;W[aq];B[cr]C[];W[bs];B[ar]C[RIGHT])
(;W[cr];B[ar]C[RIGHT]))
(;B[ds];W[bq])
(;B[hr];W[ds])
(;B[cr];W[bs];B[bq];W[ds])
(;B[bs];W[cr]C[thanks to Blyx and Kanashimi]
(;B[bq];W[as]
(;B[aq];W[ds])
(;B[ds];W[aq]))
(;B[ds];W[bq]))
(;B[hq];W[ds])
(;B[hs];W[ds])
(;B[ar];W[bq]))