(;GM[1]FF[4]CA[UTF-8]AP[CGoban:2]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PW[White]PB[Black]AW[bq][cq][ar][dr][ds]AB[bn][bp][cp][dp][eq][br][er][gr][cs]C[how to kill these white stones?]
(;B[bs]CR[bs]C[RIGHT
now white cannot make a ko, and it is a dead shape inside])
(;B[ap]CR[ap]
;W[bs]CR[bs]C[ko])
(;B[cr]CR[cr]
;W[bs]CR[bs])
(;B[dq]CR[dq]
;W[bs]CR[bs]C[ko])
(;B[es]CR[es]
;W[bs]CR[bs]C[ko])
(;B[as]CR[as]
;W[bs]CR[bs]C[ko])
(;B[aq]CR[aq]
;W[ap]CR[ap]
;B[bs]CR[bs]C[RIGHT
that first exchange is a little bad, but okay, it's still dead]))