(;
GM[1]
SZ[19]
AW[dd][cf][kc][kd][kf][lg][qc][qd][qf][rf][kq][cq][dp][fq]
AB[fc][id][jc][jf][kg][pc][pd][pe][og][qh][pp][bp][cn][ck]
TR[lg]
C[Problem 133. Black to play.  

White has just played the marked stone (see Problem 57). How should Black counter this move ? ]
;B[ke]
TE[2]
C[Correct Answer.  

Black should atari at 1. ]
;W[le]
C[White has no choice but to block with 2. ]
;B[lf];W[mf];B[kf]
C[After Black connects with 5, ... ]
;W[ne];B[pf];W[md]
C[... the sequence to 8 is inevitable. ]
;B[lh];W[mg];B[mh];W[qb];B[nc];W[mc];B[ng]
C[Black now builds a wall in the center. ]
;W[nb]
C[White can live with her stones by playing 16, but Black ends in sente. Black's thick wall in the center gives him a huge advantage. <= ]
)
)