(;
GM[1]
SZ[19]
AW[cd][fc][nc][nb][pc][qc][qm][ro][qq][nq][mp][iq][fq][fp][ck][ek][gr][jo]
AB[dp][pp][lc][me][qd][pd][od][pj][oq][np][mq][no][dn][ci][kq][eq][cm][fr][er][cf]
TR[ek]
C[Problem 160. Black to play.  

How should Black respond to the marked white stone (White 8 in the game continuation of Problem 156) ? ]
(;B[ei]
TE[2]
C[Correct Answer.  

Black should strengthen his stones in the upper left by jumping to 1. ]
(;W[gk]
C[If White jumps to 2, ... ]
;B[dd]
C[... Black can start moving against White's corner enclosure by attaching at 3 ... ]
;W[dc];B[cc]
C[... and cutting with 5. ]
;W[bd];B[bc];W[bb];B[ec];W[db];B[ed];W[eb];B[be];W[cb];B[ce];W[ac]
C[The sequence to White 16. where Black builds thickness by squeezing White, is inevitable. ]
;B[ge]
LB[gc:A]
C[Finally, Black perfects his shape with 17, threatening to attach at A. <= ]
)
(;W[ee]
C[Variation.  

If White defends her position in the upper left with 2, ... ]
;B[fk]
C[... Black can attach at 3. ]
;W[fl];B[gk];W[ej];B[fi];W[em];B[gl]
C[With the sequence to 9, Black has built thickness in the center. <= ]
))
(;B[fm]
C[How the game continued.  

Black jumped to 1, ... ]
;W[ei]
C[... letting White take the key point of 2. ]
;B[ef]
C[When Black jumped to 3, ... ]
;W[gf]
C[... White capped with 4, so ... ]
;B[bd];W[bc];B[be]
LB[bd:5]
C[... Black played 5 and 7 to make a base for his stones. ]
;W[de]
C[Next, White peeped at 8. <= ]
)
)