(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PB[Black to play]
AB[rq][rp][qo][pn][ro][mo][mp][mq][nr][mr][om][nm][mn][pp]
AW[qq][qp][po][oo][no][np][nq][or][qr]
C[This is the problem position. Black to play.]
(;B[oq]C[White has already let black put a stone inside his eye space.
Perhaps he was thinking black would play here?]
;W[pq]C[This is now two eyes already.])
(;B[rr]C[Or this?]
;W[pq]
(;B[op]
;W[ps]C[Two eyes])
(;B[ps]
;W[op]
(;B[pr]
;W[qs]
;B[os]
;W[ns])
(;B[os]
;W[qs]
;B[ns]
;W[pr]C[Again two eyes.])))
(;B[ps]C[This quickly fails too.]
;W[os])
(;B[pq]C[Adding another stone inside the eye space like
this is correct.]
(;W[rr]C[If white tries to make an eye in the corner...]
;B[pr]C[...then black must add a third stone.]
;W[ps]
;B[rs]C[Now the clamp is the tesuji.]
(;W[sr]C[If white here...]
;B[qs]C[...then black plays inside again.]
(;W[ss]
;B[qs]
;W[rs]
;B[sq]C[White runs out of liberties.])
(;W[os]
;B[sq]
;W[ss]
;B[qs]
;W[rs]C[still out of liberties.]))
(;W[os]
;B[sr]C[No corner eye.])
(;W[qs]
;B[sr]
;W[ss]
;B[sq]C[Also fails]))
(;W[ps]
;B[rr]C[white dies])
(;W[rs]
;B[pr]
;W[ps]
;B[rr]C[White dies])
(;W[pr]
;B[rr]
;W[qs]
;B[os]C[White dies.])))
