(;GM[1]FF[4]AP[Drago:4.22.03]SZ[19]CA[UTF-8]AW[rr][rq][qp][pp][pq][pr]AB[os][or][oq][op][po][qo][rn][rp][sp]C[Black to play and kill.]
(;B[sq]C[Incorrect - White lives];W[sr];B[qs];W[qr];B[ps];W[rs])
(;B[qs]C[Incorrect.]
(;W[qr];B[ps];W[rs];B[sq];W[sr])
(;W[ps]C[This is a White mistake.];B[qr];W[qq]
(;B[sq])
(;B[sr]))
(;W[rs]C[Also wrong.];B[qr]))
(;B[sr]C[Correct.];W[sq];B[qs]
(;W[qr]
(;B[rs];W[ss]
;B[ps]C[White is dead.])
(;B[ps]C[This is a mistake; White lives.];W[rs]))
(;W[rs]C[This also fails.];B[qr])))
