(;
GM[1]
SZ[19]
AW[od][qc][oq][pq][qp][qn][dp][cj]
AB[cd][ed][jc][qd][op][nq][np][cn][iq]
LB[kq:D][co:C][cl:B][cg:A]
TR[cn]
C[Problem 144. White to play.  

Black has played the marked stone, separating the white stones on the left. Black has strong positions above and below, so attacking this stone in not a good idea. Where should White play ? ]
(;W[cg]
TE[2]
C[Correct Answer.  

White should extend to 1, strengthening her weakest stone. ]
;B[fq]
C[Next, Black will approach with 2 and ... ]
;W[fp]
C[... White responds by attaching with 3. ]
;B[gp];W[eq];B[fo];W[ep]
C[After White 7, all of White's stones are secure. <= ]
)
(;W[co]
C[Failure.  

If White defends her corner with 1 ... ]
;B[dn];W[fq]
C[... and 3, the white stone on the side will come under attack ... ]
;B[ch]
C[... when Black extends from his corner enclosure with 4. ]
;W[ej];B[fn]
C[After 6, Black has taken the lead. <= ]
)
)