(;GM[1]FF[4]AP[Drago:4.22.03]SZ[19]CA[UTF-8]AW[rr][rq][sp][ro][qo][po][oo][no][mo][mp][lq][lr][mr][ps]AB[mq][nr][nq][np][op][pp][qp][rp][qq][pr]C[Black to play and live.]
(;B[oq]C[Incorrect.];W[os]
(;B[qr]
;W[ns]C[Black is dead.])
(;B[ns]
;W[qr]C[Black is dead.]))
(;B[os]C[Correct.];W[oq];B[qr];W[qs]
(;B[sr]C[This is the move that 
traps white corner stones.]
(;W[sq];B[rs]
(;W[so];B[qs])
(;W[ss];B[qs]))
(;W[rs];B[sq]))
(;B[rs]C[This is a mistake.];W[qs];B[sr]
;W[ss]C[This is a Ko.])))
