(;GM[1]FF[4]SZ[19]
GN[Main line]
PC[http://senseis.xmp.net/?BeginnerExercise208/Solution]AP[GoWiki:2009]
DT[2009-04-22]
C[Diagram from http://senseis.xmp.net/?BeginnerExercise208/Solution

Main line]
PL[B]

AB[ac][be][bf][cf][bg][dg][bh][ch][dh][bi]
AW[bb][bd][cd][ae][ce][af][df][ef][eg][eh][ci][di][ei][bj][ck]

;B[ai]C[B1]MN[1]
;W[ad]C[W2]MN[2]
;B[ag]C[B3]MN[3]

;
)
