(;
GM[1]
SZ[19]
AW[cf][ci][ic][ie][nc][nd]
AB[cd][dd][gc][ge][oc][pd][pf]
TR[ie][ge]
C[Problem 24.  Black to play.  

White and Black have exchanged the marked stones. Where is Black's invasion point now ? ]
(;B[jd]
TE[2]
C[Correct Answer.  

Black should first peep at 1, ... ]
;W[id];B[ld]
C[... then play on the vital point of 3. ]
;W[nf]
C[When White jumps to 4, ... ]
;B[lf]
C[... Black jumps to 5. Black can now attach on either the left or the right. <= ]
)
(;B[kc]
C[Failure.  

Invading deeply at 1 could be disastrous for Black ... ]
;W[ke]
C[... after White caps with 2. <= ]
)
)