(;GM[1]FF[4]SZ[19]
GN[White's threat]
PC[http://senseis.xmp.net/?BeginnerExercise234/Solution]AP[GoWiki:2009]
DT[2009-04-22]
C[Diagram from http://senseis.xmp.net/?BeginnerExercise234/Solution

White's threat]
PL[B]

AB[ih][jh][kh][hi][ji][li][hj][jj][lj]
AW[ig][jg][kg][gh][hh][lh][mh][gi][mi][gj][mj][gk][mk][hl][il][jl][kl][ll]

;B[ij]C[B1]MN[1]
;W[kj]C[W2]MN[2]
;B[kk]C[B3]MN[3]
;W[jk]C[W4]MN[4]

;
)
