(;GM[1]FF[4]AP[Drago:4.22.03]SZ[19]CA[UTF-8]AB[rs][rr][qq][pq][po][qo][on][nn][mn][lo][lp][lq][lr]AW[no][oo][mp][mq][mr][nq][oq][ns][pr][qr]C[Black to play and kill.]
(;B[op]
;W[or]C[Incorrect.])
(;B[qs]C[Incorrect.];W[or])
(;B[ps]C[Incorrect.];W[or];B[qs])
(;B[or]C[Correct. This is the vital point for both sides.]
(;W[ps]
;B[op]C[White is dead.])
(;W[os]C[This is a mistake by White - Black can tenuki.];B[rn]
(;W[op];B[ps])
(;W[nr];B[qs]
(;W[op];B[ps])
(;W[ps];B[op])))))
