(;
GM[1]
SZ[19]
AW[dd][dg][cn][dp][jp][no][nq][nr][oe]
AB[oq][pp][pn][nm][qj][oc][qd][pe][id][fc]
LB[pe:2][oe:1]
C[Problem 158. White to play.  

The attachment of Black 2 is a move used in special situations. It is a move contrary to the go principle of not attaching against attacking stones. But in this case, Black's corner is strong and he is not worried about eyes. Try to read five moves ahead. ]
;W[od]
TE[2]
C[Correct Answer.  

By bumping against Black with 1, White is looking for a way to make shape. ]
;B[nc]
C[Black 2 is absolutely necessary. ]
;W[pf]
C[After that, White 3 ... ]
;B[pd]
(;W[ng]
C[... and 5 make good shape. <= ]
)
(;W[og]
C[Failure.  

White 5 here would create a heavy shape. <= ]
)
)