(;
GM[1]
SZ[19]
AW[bd][cf][ci][kc][ld][md][ne][od][qd][qc]
AB[dd][cc][fd][ic][qb][nc][nd][mc]
LB[qc:1]
C[Problem 123. Black to play.  

How does Black respond when White bumps into his stone with 1 ? ]
(;B[oc]
TE[2]
C[Correct Answer.  

Black 1 is the vital point. ]
(;W[rb];B[kb];W[jb];B[lb];W[jc];B[pb]
LB[oe:A]
C[Black lives with the moves to 7. Black now aims to cut at A. <= ]
)
(;W[pb]
C[If White 2 here, ... ]
;B[pc]
C[... Black plays 3 and he can break through White's wall. <= ]
))
(;B[pb]
C[Failure.  

Black can live by drawing back with 1, ... ]
;W[oc];B[ob];W[rb];B[lb];W[kb];B[na]
C[... but he has a smaller life and doesn't leave weaknesses in White's position. <= ]
)
)