(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PB[Black to play]C[Just play through the moves to move 24 which is the problem position. These do not represent a game sequence!]
;B[qq]
;W[qr]
;B[qp]
;W[rq]
;B[pp]
;W[pq]
;B[op]
;W[oq]
;B[nq]
;W[or]
;B[nr]
;W[rp]
;B[pn]
;W[ro]
;B[om]
;W[np]
;B[mn]
;W[mp]
;B[lp]
;W[lq]
;B[lo]
;W[kr]
;B[]
;W[jq]C[This is the problem position. Black to play.]
(;B[mq]C[The cut doesn't work]
;W[mr]
(;B[no]
;W[ns])
(;B[ns]
;W[ms]
;B[no]
;W[os]))
(;B[os]
;W[pr]
;B[mq]
;W[mr]C[Playing the atari first does not help])
(;B[ms]C[This looks clever]
;W[mr]
;B[pr]
(;W[os]
;B[ns]
;W[ps]C[But black quickly runs out of liberties])
(;W[ps]C[This would be a mistake for white]
;B[os]
;W[ns]C[As a ko developes]
;B[dd]C[ko threat]
;W[cd]
;B[os]
;W[pr]
;B[rr]C[Connecting is still a ko]
;W[ns]))
(;B[ns]C[This is the correct move]
(;W[mq]C[If white connects ]
;B[pr]
;W[ps]
;B[os]
;W[pr]
;B[rr]C[Then the throw-in by black catches the white stones.])
(;W[os]C[This white doesn't work either]
;B[ps]
;W[pr]
;B[rr]
;W[qs]
;B[rs]C[Again white runs out of liberties.])
(;W[pr]C[If white defends the weakness]
;B[mq]
;W[ms]
;B[no]
;W[mr]
;B[mo]C[Then black can cut and win the capturing race.])))
