(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PW[White to play]C[Just play through the moves to move 20 which is the problem position. These do not represent a game sequence!]
;B[bc]
;W[cc]
;B[cb]
;W[cd]
;B[bd]
;W[be]
;B[dc]
;W[dd]
;B[eb]
;W[ed]
;B[fb]
;W[fd]
;B[]
;W[gb]
;B[]
;W[gc]
;B[]
;W[ga]
;B[]
;W[cf]C[This is the problem position. White to play.]
;B[]
;W[bb]C[If anything works it has to be this move which is
correct.]
;B[ab]
;W[ba]C[Whaite must add a second stone to keep the eyes
down to one.]
;B[ca]
;W[ad]
;B[aa]C[Next white can throw in]
;W[bb]
;B[ba]
;W[ae]C[and threaten the corner eye]
;B[ac]
;W[db]C[And another throw in...]
;B[da]
;W[fa]C[... leaves the second eye false. Black needs two 
moves to make it.])
