(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PB[Black to play]AW[kp][lp][op][kq][nq][oq][kr][lr][or]AB[ko][lo][mo][no][oo][qo][hp][jp][np][pp][jq][lq][jr][pr][qr]C[This is the problem position. Black to play]
(;B[mq]C[Adding another potential captured stone
is the tesuji.]
;W[mp]
;B[os]C[The hane here is crucial.]
;W[ns]
;B[mr]C[And black adds a third stone inside,
which either kills by shortage of liberties
or bulky eye]
(;W[ks]
;B[ms]C[White cannot atari on either side.])
(;W[ms]
;B[ks]C[This is a dead shape. ]
;W[nr]
;B[mq]))
(;B[ks]C[This move doesn't kill.]
;W[mq]
(;B[ns]
;W[os]
;B[ls]
;W[ms]
;B[mr]
;W[nr])
(;B[ms]
;W[ns]
;B[ls]
;W[mr]))
(;B[os]C[Nor does this kill.]
;W[mq]
;B[ks]
;W[ns]
;B[ms]
;W[mr]
;B[nr]
;W[ls])
(;B[ns]
;W[mq]C[After capturing the single stone,
black cannot ever take away the edge eye. ]
;B[os]
;W[ms]
;B[nr]
;W[ks]))
