(;GM[1]FF[4]SZ[19]
GN[W7 starts a huge ko]
PC[http://senseis.xmp.net/?GokyoSeimyoVolume3Problem5/Attempts]AP[GoWiki:2009]
DT[2009-04-25]
C[Diagram from http://senseis.xmp.net/?GokyoSeimyoVolume3Problem5/Attempts

W7 starts a huge ko]
PL[W]

AB[jb][kb][pb][rb][jc][lc][mc][nc][oc][qc][rd][sd]
AW[ob][kc][pc][kd][ld][md][nd][od][pd][qd][re][se][qf]

;W[sb]C[W1]MN[1]
;B[rc]C[B2]MN[2]
;W[pa]C[W3]MN[3]
;B[qb]C[B4]MN[4]
;W[lb]C[W5]MN[5]
;B[nb]C[B6]MN[6]
;W[na]C[W7]MN[7]

;
)
