(;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]))