Problem	4304
Created	2004-04-18
Name	BartTM's oversight
Source	Variation on problem 4300 by Lok.
Rating

Difficulty	7 dan
Average Solve Time	46 secs
User Attempts	341 / 2728
Solve Ratio Rating	2 dan
	rating history

This is a variation on problem 4300 by Lok. With thanks to wheezy and goodness ;)

(;AB[ab]AB[bb]AB[cc]AB[bd]AB[be]AB[ce]AB[df]AB[ef]AB[ee]AB[ed]AB[fd]AB[fc]AB[fb]AB[fa]AW[ea]AW[eb]AW[ec]AW[dc]AW[dd]AW[de]AW[cb]AW[ba]AW[cf]AW[bf]AW[ch]AW[dg]AW[eh]AW[ae]TR[ae]C[I thought the triangled move would let White live unconditionally. Show me why that's not true!]AW[bh]AP[goproblems] (;B[aa];W[bc] (;B[ac];W[cd] (;B[ca];W[bc]C[Thanks to A19 Black has a chance to kill White with ko.RIGHT]) (;B[da];W[bc]C[Thanks to A19 Black has a chance to kill White with ko.RIGHT]) (;B[db];W[da] (;B[ca];W[bc]C[Dead in double ko.]) (;B[bc];W[ad]) (;B[ad];W[bc])) (;B[bc];W[ad]) (;B[ad];W[bc])) (;B[ca];W[cd]) (;B[ad];W[ac]) (;B[db];W[ac]) (;B[cd];W[ad]) (;B[da];W[ac])) (;B[ad];W[af] (;B[cd];W[da]C[White is alive in seki. If Black plays A19 White kills Black at A17.]) (;B[bc];W[da]C[White is alive in seki.]) (;B[aa];W[cd] (;B[ca];W[bc]) (;B[bc];W[ac]) (;B[da];W[bc]) (;B[db];W[bc]) (;B[ac];W[bc])) (;B[ac];W[da] (;B[aa];W[cd];B[ca];W[bc]C[Black is dead in double ko.]) (;B[cd]C[White lives in seki.])) (;B[ca];W[da] (;B[aa];W[cd] (;B[ca];W[bc]) (;B[bc];W[ac]) (;B[ac];W[bc])) (;B[cd]C[White is alive in seki. If Black plays A19 White kills Black at A17.]) (;B[bc]C[White lives in seki.]) (;B[ac];W[cd])) (;B[da];W[bc] (;B[cd];W[ac]) (;B[ac];W[ca] (;B[cd];W[db]C[White lives in seki.]) (;B[aa];W[db]C[White lives in seki.])) (;B[aa];W[ac]) (;B[ca];W[cd]) (;B[db];W[ca] (;B[ac];W[cd]) (;B[db];W[cd]) (;B[da];W[cd]) (;B[cd];W[ac]) (;B[aa];W[ac]))) (;B[db];W[da] (;B[aa];W[cd] (;B[ca];W[bc]) (;B[bc];W[ac]) (;B[ac];W[bc])) (;B[cd]C[White is alive in seki. If Black plays A19 White kills Black at A17.]) (;B[bc]C[White lives in seki.]) (;B[ac];W[cd]))) (;B[cd];W[ad];B[bc];W[da]C[Black is dead.]) (;B[ac];W[da] (;B[cd];W[af] (;B[aa];W[ad];B[ca];W[bc]) (;B[ad]C[White lives in seki.])) (;B[ad];W[af] (;B[aa];W[cd];B[ca];W[bc]C[Black is dead in double ko.]) (;B[cd]C[White lives in seki.])) (;B[aa];W[cd] (;B[ca];W[bc]C[Dead in double ko.]) (;B[bc];W[ad]) (;B[ad];W[bc]))) (;B[bc];W[ad]) (;B[ca];W[da] (;B[aa];W[bc] (;B[ac];W[cd]) (;B[cd];W[ad]) (;B[ad];W[ac]) (;B[ca];W[cd])) (;B[cd];W[ad]) (;B[bc];W[ad]) (;B[ad];W[bc] (;B[ac];W[af]) (;B[cd];W[ac]) (;B[aa];W[ac]) (;B[af];W[cd] (;B[ac];W[cc]C[Black loses the capturing race.]) (;B[ae];W[ag]) (;B[aa];W[ac]))) (;B[ac];W[cd] (;B[ad];W[af]) (;B[bc]) (;B[aa]C[White is alive. White can even pass now. If Black takes at C19 White kills Black in double ko at B17.]))) (;B[da];W[ad] (;B[ca];W[db] (;B[ca];W[ac]C[White lives in seki.]) (;B[bc];W[ca]) (;B[cd];W[bc]) (;B[ac];W[af] (;B[ca]C[White lives in sente with seki.]) (;B[cd];W[bc]) (;B[aa];W[bc]) (;B[da];W[ca]) (;B[bc];W[ca])) (;B[aa];W[bc] (;B[ca];W[cd]) (;B[ac];W[bc]))) (;B[cd];W[bc]) (;B[bc];W[ca] (;B[aa];W[db]) (;B[cd];W[db]) (;B[ac];W[af])) (;B[ac];W[af] (;B[ca];W[db] (;B[ca]C[White lives in sente with seki.]) (;B[cd];W[bc]) (;B[aa];W[bc]) (;B[da];W[ca]) (;B[bc];W[ca])) (;B[cd];W[bc]) (;B[bc];W[ca]) (;B[db];W[ca]) (;B[aa];W[bc])) (;B[aa];W[bc] (;B[ac];W[bc]) (;B[ca];W[cd]) (;B[db];W[cd])) (;B[db];W[ca])) (;B[db];W[da] (;B[aa];W[bc] (;B[ac]) (;B[cd];W[ad]) (;B[ad];W[ac]) (;B[ca];W[cd])) (;B[cd];W[ad]) (;B[bc];W[ad]) (;B[ad];W[bc] (;B[ac]) (;B[cd];W[ac]) (;B[aa]) (;B[af];W[cd] (;B[ac];W[cc]C[Black loses the capturing race.]) (;B[ae];W[ag]) (;B[aa];W[ac]))) (;B[ac];W[cd] (;B[ad];W[af]) (;B[bc]) (;B[aa]C[White is alive. White can even pass now. If Black takes at C19 White kills Black in double ko at B17.]))) (;B[af];W[ag] (;B[aa];W[bc] (;B[ac];W[cd] (;B[ca];W[bc]C[Black now has a chance to kill White with ko.RIGHT]) (;B[da];W[bc]C[Black now has a chance to kill White with ko.RIGHT]) (;B[db];W[da];B[ca];W[bc]C[Double ko; black is dead.])) (;B[ca];W[cd]) (;B[da];W[cd]) (;B[db];W[ac]) (;B[ad];W[ac]) (;B[cd];W[ac])) (;B[ca];W[da] (;B[aa];W[bc] (;B[ac];W[cd];B[ca];W[bc]C[Double ko; black is dead.]) (;B[ca];W[cd]) (;B[ad];W[ac])) (;B[cd];W[ad]) (;B[bc];W[ad]) (;B[ac];W[cd] (;B[aa]C[Black is dead; even if White passes now, Black dies in double ko after Black C19, White B17.]) (;B[ad];W[af])) (;B[ad];W[bc];B[ac];W[cd];B[af];W[bc]C[Black is dead in double ko.])) (;B[da];W[ad] (;B[ca];W[db] (;B[ca];W[ac]C[White lives in seki.]) (;B[bc];W[ca]) (;B[ac];W[af];B[ca]C[White lives in seki.]) (;B[aa];W[bc] (;B[ca];W[cd]) (;B[ac];W[bc]))) (;B[ac];W[af] (;B[bc];W[ca]) (;B[ca];W[db];B[ca]C[White lives in seki.]) (;B[db];W[ca])) (;B[bc];W[ca])) (;B[db];W[da] (;B[aa];W[bc] (;B[ac];W[cd]) (;B[ca];W[cd]) (;B[ad];W[ac])) (;B[cd];W[ad]) (;B[bc];W[ad]) (;B[ac];W[cd] (;B[aa]C[Black is dead; even if White passes now, Black dies in double ko after Black C19, White B17.]) (;B[ad];W[af])) (;B[ad];W[bc];B[ac];W[cd];B[af];W[bc]C[Black is dead in double ko.])) (;B[ad];W[bc] (;B[ac];W[cd];B[af];W[bc]C[Black is dead with double ko.]) (;B[af];W[cd];B[ac];W[cc]) (;B[ca];W[cd]) (;B[db];W[cd]) (;B[da];W[cd])) (;B[cd];W[ad]) (;B[ac];W[da] (;B[cd];W[af] (;B[aa];W[ad];B[ca];W[bc]) (;B[ad])) (;B[ad];W[cd];B[af];W[bc]C[Black is dead in double ko.]) (;B[aa];W[cd]) (;B[bc];W[cd])) (;B[bc];W[ad] (;B[da];W[ca]) (;B[cd];W[da]) (;B[aa];W[ca]) (;B[ac];W[af]) (;B[ca];W[da]) (;B[db];W[da])) (;B[bg];W[ad])))