(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]RU[Japanese]SZ[19]KM[0.00]PB[Black to play]AW[mo][no][oo][po][qo][ro][mp][mq][oq][pq][lr][nr][pr]AB[np][op][pp][qp][nq][qq][rq][mr][qr]C[Black to play and live.]
(;B[sr]C[Black needs both 2-1 points or to capture something to live.];W[rs];B[qs];W[ms];B[or];W[os];B[ps]
;W[or]C[That 2-1 and it dies])
(;B[rs]C[This 2-1 is correct];W[sr]
(;B[or];W[os];B[ps]
;W[qs]C[It's a Ko to live.])
(;B[ms]C[If Black adds a stone here,];W[ns]C[then White must not block this side.];B[ps]))
(;B[or]C[Also a Ko if here first.];W[os];B[rs];W[sr];B[ps];W[qs]))
