(;GM[1]FF[4]SZ[19]
GN[Black (3) is strongest if white defends at (2)]
PC[http://senseis.xmp.net/?GokyoShumyoSection3Problem51/Attempts]AP[GoWiki:2009]
DT[2011-01-05]
C[Diagram from http://senseis.xmp.net/?GokyoShumyoSection3Problem51/Attempts

Black (3) is strongest if white defends at (2)]
PL[B]

AB[ib][bc][cc][ic][ad][bd][be][ce][ee][ge][he][ef]
AW[bb][cb][hb][ac][dc][gc][cd][dd][gd]

;B[fb]C[B1]MN[1]
;W[fc]C[W2]MN[2]
;B[eb]C[B3]MN[3]
;W[gb]C[W4]MN[4]
;B[db]C[B5]MN[5]
;W[ab]C[W6]MN[6]
;B[ca]C[B7]MN[7]

;
)
