(;GM[1]FF[4]SZ[19]AP[SmartGo:0.8.7]CA[utf-8]
GN[prob_779]
AB[qm:rm][pn:po][oo:oq][qp:qq][pq][rr:sr]
AW[pl:pm][ql][nm][qn:rn][no:nq][rq:sq][or:qr][rs]
C[Black plays.

Source:
"Tesuji Problems"
Go World #26, p. 22,  Winter 1981]
(;B[sp]
C[Starting with the atari is a mistake.];W[ss];B[sn]
C[Black can try to connect by wrapping around, but ...];W[rl];B[sm];W[sl]
;B[so];W[rp]
C[... White wins the semeai.])
(;B[sn]
C[Black's hane seems unlikely to work, but is the only move!];W[rl];B[sm]
;W[so]
C[White seems to eliminate the aji with this atari, but ...];B[sp];W[rp]
;B[ro]
C[... after this throw-in, Black has a double atari and a snap-back!  Black makes a 2nd eye.]
))

