(;GM[1]FF[4]SZ[19]
GN[Block]
PC[http://senseis.xmp.net/?EndgameTesuji2/WhyIsTheMarkedStoneNecessary]AP[GoWiki:2009]
DT[2009-04-22]
C[Diagram from http://senseis.xmp.net/?EndgameTesuji2/WhyIsTheMarkedStoneNecessary

Block]
PL[B]

AB[dc][dd][de]
AW[eb][ec][ed][gd][ee]

;B[db]C[B1]MN[1]
;W[da]C[W2]MN[2]
;B[ca]C[B3]MN[3]
;W[ea]C[W4]MN[4]
;B[cb]C[B5]MN[5]

;
)
