(;
GM[1]
SZ[19]
AW[dd][hc][pb][oc][pd][pe][of][qo][qm][eq][fp][jq][mq]
AB[kc][qb][qc][qd][qe][qg][pc][pq][op][pn][cj][cp][do]
C[Problem 51. Black to play.  

The middle game has begun. How should Black attack ? ]
(;B[nc]
TE[2]
C[Correct Answer.  

Black expands his position with 1 ... ]
;W[ob];B[nd]
C[... and 3, leaving White's stones heavy. ]
;W[od];B[lf]
C[He then makes shape with 5, ... ]
;W[oh]
C[... forcing White to escape with 6. ]
;B[qp]
C[Next, Black attaches with 7. White's stones are now unsettled, while Black's are secure. <= ]
)
(;B[qp]
C[Failure.  

If Black immediately attaches with 1, ... ]
;W[mc]
C[... White can make shape by taking the vital point of 2. The black stone at the top is now isolated and weak. <= ]
)
)
