(;
GM[1]
SZ[19]
AW[dd][dp][nq][qq]
AB[cj][lq][pp][pd]
LB[pj:A][nq:1][lq:2][qq:3]
TR[cj]
C[Problem 6. Black to play.  

Instead of making a sanren-sei at A, Black has played the marked stone. When White plays 3, in which direction should Black block ? ]
(;B[pq]
TE[2]
C[Correct Answer.  

Blocking from the left side with Black 1 is the correct direction. ]
;W[qp];B[po];W[pr];B[or];W[qr];B[oq];W[qn]
C[The sequence to White 8 is a joseki. Even though White has taken profit, Black is happy with his thickness. Moreover, he still retains sente. <= ]
)
(;B[qp]
C[Failure.  

If Black does not have a stone in the middle of the right side, he should not block from above ... ]
;W[pq];B[op];W[nr];B[mo]
C[... and play this joseki ... ]
;W[qj]
C[... because White 6 eases the influence of Black's wall below. <= ]
)
)