(;
GM[1]
SZ[19]
AW[nc][dm][cf][hc][cd][bc][de][be][ch][kb]
AB[pj][dj][dp][pd][pp][dd][pf][fp][fd][dg][cc][bb][ed][ac][kd]
TR[kd][kb]
C[Problem 77. Black to play.  

After the exchange of the marked black and white stones (Black 1 - White 2 in Problem 73), where should Black play ? ]
(;B[ei]
TE[2]
C[Correct Answer.  

Black 1 is a thick move which defends the marked stone and attacks the white stones above and below. ]
;W[gm]
LB[ff:C][ef:B][ad:A]
C[Jumping to White 2 next is the best move. The white stones in the upper left are quite resilient since White can start a ko at A. If White escapes into the center with B, Black will attach at C and he'll get a thick wall in the center. <= ]
)
(;B[ef]
C[How the game continued.  

Black played the diagonal move of 1, but ... ]
;W[cj]
C[... this allowed White to attach with 2, ... ]
;B[ck];W[dk]
LB[ei:A]
C[... then cut with 4, throwing the left side into a free-for-all fight. Playing 1 in the Correct Answer (A here) prevents White from making sabaki on the left side. <= ]
)
)