(;
GM[1]
SZ[19]
AW[dc][pc][dp]
AB[ce][qe][pp]
LB[ce:1][pc:2]
C[Problem 85. Black to play.  

An approach move at White 2 would seem to be common sense to prevent Black from making a corner enclosure. But White 2 is a mistake. How should Black punish White ? ]
;B[od]
TE[2]
C[Correct Answer.  

Black should press White with 1 ... ]
;W[oc];B[nd]
C[... and 3, ... ]
;W[mc];B[ed]
C[... followed by 5 ... ]
;W[ec];B[fd]
C[... and 7. ]
;W[gc]
(;B[pj]
LB[od:1]
TR[pc]
C[He then extends along the right side with 9.  

If White wants to make an approach move, the high approach at 1 (instead of the marked stone) would give her a better result. <= ]
)
(;B[nc]
C[Overconcentrated.  

Black could also force White's stones at the top to become overconcentrated with the forcing sequence from 9 ... ]
;W[nb];B[mb];W[lb];B[md];W[lc];B[ob];W[ma];B[qc];W[pb];B[fc];W[fb];B[gb];W[hb];B[gd];W[hc];B[eb];W[ga];B[cc]
C[... to 27. ]
;W[db];B[pj]
C[Black now has a big lead. <= ]
)
)