Problem	7098
Created	2005-08-16
Source	Problem 7040
Rating

Difficulty	7 dan
Average Solve Time	48 secs
User Attempts	94 / 1201
Solve Ratio Rating	4 dan
	rating history

Let's suppose Black has a big ko threat somewhere else, and White doesn't. Now find the best continuation.

(;AB[ob]AB[nb]AB[nd]AB[od]AB[oe]AB[pf]AB[pg]AB[rg]AB[rf]AB[re]AW[pb]AW[pc]AW[pd]AW[pe]AB[pa]AB[qd]AW[qe]AW[rd]TR[pa]C[Grebble found this nice attack against the corner.]AP[goproblems] (;W[rb];B[ra] (;W[qc];B[sc] (;W[qa];B[qb] (;W[sb];B[sd] (;W[qa]MA[oa]C[Black has to find the first ko threat elsewhere, and White has an extra ko threat at P19 to boot.RIGHT]) (;W[se];B[qa]) (;W[sa];B[rc]) (;W[oa];B[na]C[];W[qa]C[Ko, Black has to find the first threat. This is nearly as good as the solution, in which White has an extra internal ko threat.]) (;W[rc];B[qa])) (;W[qa]C[NOTTHIS]) (;W[sd];B[sb] (;W[qa]MA[sd]MA[sb]C[Black has to find a ko threat somewhere else. The T16-T18 exchange gets a few points more than T18-T16, but now White doesn't have the extra ko threat at P19.]MA[oa]) (;W[rc];B[qa]) (;W[oa];B[rc];W[qa];B[se] (;W[rb];B[qd]) (;W[qd];B[rb] (;W[sa];B[rb]MA[rc]MA[sb]) (;W[pa]C[White is dead. If White captures, Black throws in at S18.]MA[rb])))) (;W[sa];B[sb] (;W[qa]C[Ko, Black has to find the first threat. In the solution White has an internal ko threat; here there isn't one so this is not as good.]) (;W[rc];B[qa]) (;W[sd];B[rc])) (;W[rc];B[qa] (;W[sd];B[sb]) (;W[sb];B[sd])) (;W[oa];B[na]C[This just wastes a ko threat.])) (;W[sd];B[sb] (;W[qa];B[qb]C[Since a ko where Black takes first is not as good as the solution, White wants to find something better than a ko threat elsewhere.] (;W[oa];B[rc];W[qa];B[se] (;W[rb];B[qd]) (;W[qd];B[rb] (;W[sa];B[rb]MA[rc]MA[sb]) (;W[pa]C[White is dead. If White captures, Black throws in at S18.]MA[rb]))) (;W[qa]C[NOTTHIS]) (;W[rc];B[qa])) (;W[qb];B[qa]) (;W[rc];B[qa] (;W[sa];B[sb]) (;W[oa];B[na];W[sa];B[sb])) (;W[oa];B[qa] (;W[rc];B[na];W[sa];B[sb]) (;W[qb];B[na]))) (;W[qb];B[qa]) (;W[sb];B[sd] (;W[qa];B[qb] (;W[sa];B[rc]) (;W[rc];B[qa]) (;W[se];B[qa]) (;W[oa];B[na]C[];W[qa]C[Ko, Black has to find the first threat. This is nearly as good as the solution, in which White has an extra internal ko threat.])) (;W[qb];B[qa]) (;W[rc];B[qa];W[se];B[sd]) (;W[sa];B[qa]) (;W[oa];B[qa]) (;W[se];B[qa])) (;W[rc];B[qa] (;W[sd];B[sb] (;W[sa];B[sb]) (;W[oa];B[na];W[sa];B[sb])) (;W[sb];B[sd];W[se];B[sd])) (;W[sa];B[qa] (;W[sb];B[sd]) (;W[sd];B[sb]) (;W[qb];B[sb]) (;W[oa];B[sb])) (;W[oa];B[qa] (;W[sa];B[sb]) (;W[qb];B[na]) (;W[sb];B[sd]) (;W[sd];B[sb] (;W[rc]) (;W[qb];B[na])))) (;W[qb];B[qa] (;W[qc];B[sc]) (;W[sd];B[sb] (;W[qc];B[sc]) (;W[sc];B[qc])) (;W[sc];B[qc]) (;W[sb];B[sd]) (;W[oa];B[na] (;W[sc];B[qc]) (;W[qc];B[sc]) (;W[sd];B[sb] (;W[qc];B[sc]) (;W[sc];B[qc])) (;W[sb];B[sd])) (;W[sa];B[oa] (;W[sd];B[sb] (;W[sc];B[qc]) (;W[qc];B[sc])) (;W[qc];B[sc] (;W[sd];B[sb]) (;W[sb];B[sd])) (;W[sc];B[qc]) (;W[sb];B[sd]))) (;W[qa];B[qb] (;W[qc];B[sb] (;W[sc];B[rc]C[Ko, White has to find the first ko threat.]) (;W[qa]C[Ko, Black has to find the first ko threat. This is almost as good as the solution in which White also has an internal ko threat.]) (;W[rc];B[qa]) (;W[sd];B[qa]) (;W[oa];B[rc] (;W[qa];B[sd] (;W[rb];B[sc]) (;W[se];B[sc]) (;W[qd];B[rb]) (;W[pa];B[rb])) (;W[sd];B[na]) (;W[sc];B[sd]))) (;W[rc];B[qa]) (;W[sc];B[qc]) (;W[sb];B[qc]) (;W[sd];B[qc]) (;W[sa];B[sb] (;W[qc];B[rc]) (;W[rc];B[qa]) (;W[sc];B[rc]))) (;W[rc];B[qa]) (;W[sb];B[qc] (;W[qb];B[qa] (;W[sd];B[rc];W[sc];B[qc]) (;W[rc];B[sd]) (;W[sa];B[oa] (;W[sd];B[rc];W[sc];B[qc]) (;W[rc];B[sd])) (;W[oa];B[na] (;W[sd];B[rc];W[sc];B[qc]) (;W[rc];B[sd]) (;W[sa];B[oa] (;W[sd];B[rc];W[sc];B[qc]) (;W[rc];B[sd])))) (;W[rc];B[qa] (;W[qb];B[sd]) (;W[sa];B[sd]) (;W[oa];B[na];W[sa];B[oa];W[qb];B[sd]) (;W[sd];B[qb])) (;W[qa];B[qb]) (;W[sd];B[qb]) (;W[sa];B[rc] (;W[sd];B[se]) (;W[sc];B[sd]) (;W[qb];B[sd]))) (;W[sd] (;B[qa]) (;B[qc] (;W[qb];B[qa] (;W[sb];B[rc];W[sc];B[qc]) (;W[rc];B[sb])) (;W[rc];B[sb] (;W[qb];B[qa]) (;W[qa];B[qb];W[qa];B[qb]) (;W[sc];B[qa])) (;W[sb];B[qb]) (;W[qa];B[qb]))) (;W[sc];B[qc] (;W[qb];B[qa]) (;W[qa];B[qb]) (;W[rc];B[qa])) (;W[sa];B[qa] (;W[qc];B[sc] (;W[sb];B[sd]) (;W[sd];B[sb]) (;W[qb];B[sb]) (;W[oa];B[sb])) (;W[qb];B[oa] (;W[sd];B[sb] (;W[sc];B[qc]) (;W[qc];B[sc])) (;W[qc];B[sc] (;W[sd];B[sb]) (;W[sb];B[sd])) (;W[sc];B[qc]) (;W[sb];B[sd])) (;W[sd];B[sb]) (;W[sb];B[qc] (;W[qb];B[oa] (;W[sd];B[rc];W[sc];B[qc]) (;W[rc];B[sd])) (;W[rc];B[sd]) (;W[sd];B[qb])) (;W[sc];B[qc])) (;W[oa];B[qa] (;W[qc];B[sc] (;W[sa]) (;W[qb];B[na]) (;W[sb];B[sd]) (;W[sd];B[sb])) (;W[qb];B[na] (;W[sc];B[qc]) (;W[qc];B[sc]) (;W[sd];B[sb] (;W[qc];B[sc]) (;W[sc];B[qc])) (;W[sb];B[sd])) (;W[sd];B[qc] (;W[qb];B[na] (;W[rc];B[sb]) (;W[sb];B[rc];W[sc];B[qc])) (;W[rc];B[na] (;W[sa];B[sb]) (;W[qb];B[sb]) (;W[sb];B[qb])) (;W[sb];B[qb]) (;W[sa];B[sb];W[qb];B[na])) (;W[sa];B[sb] (;W[qb];B[na] (;W[sc];B[qc]) (;W[qc];B[sc])) (;W[qc];B[sc]) (;W[sc];B[qc] (;W[sa];B[na]) (;W[qb];B[na]))) (;W[sc];B[qc] (;W[qb];B[na]) (;W[sa];B[na])))) (;W[qa];B[rc] (;W[qc];B[rb] (;W[sd];B[sc] (;W[ra];B[se] (;W[qd];B[sb]) (;W[sb];B[qd]) (;W[qb];B[qd])) (;W[sb];B[se] (;W[qd];B[sa]C[White is dead. Black can take all outside liberties, then give atari at S19. If White plays S19 or R18 White plays T18 to create a 5 stone nakade shape.]) (;W[ra];B[qd]) (;W[qb];B[qd]) (;W[sa];B[qd]) (;W[oa];B[qd])) (;W[qb];B[se] (;W[qd];B[sb]) (;W[ra];B[qd]) (;W[sb];B[qd])) (;W[qd];B[oa];W[qb];B[sb]) (;W[oa];B[se] (;W[qd]C[White is dead. Black can take all outside liberties, then give atari at S19. If White plays T19, S19 or R18 White plays T18 to create a 4 stone nakade shape. T19 then T18 etc.]) (;W[sb];B[qd]) (;W[ra];B[qd]) (;W[qb];B[qd]))) (;W[sc];B[sb] (;W[sd];B[se] (;W[qd];B[ra]MA[rb]C[If White captures the Black stones Black will play S18 to reduce the corner group to one eye.]) (;W[oa];B[qd]) (;W[ra];B[qd])) (;W[oa];B[sd])) (;W[oa];B[sd]) (;W[ra];B[sd]) (;W[qb];B[sd])) (;W[sd];B[qc]) (;W[rb];B[qc]) (;W[oa];B[qc])) (;W[qb];B[rc] (;W[sd];B[sc];W[qc];B[se];W[qd];B[qa] (;W[ra];B[sb];W[oa];B[pa]) (;W[rb];B[ra]) (;W[sb];B[ra])) (;W[qc];B[sd];W[rb];B[sc])) (;W[qc];B[rb] (;W[qa];B[rc] (;W[sd];B[sc] (;W[ra];B[se] (;W[qd];B[sb]) (;W[sb];B[qd]) (;W[qb];B[qd])) (;W[sb];B[se] (;W[qd];B[sa]C[White is dead. Black can take all outside liberties, then give atari at S19. If White plays S19 or R18 White plays T18 to create a 5 stone nakade shape.]) (;W[ra]) (;W[qb];B[qd]) (;W[sa];B[qd]) (;W[oa];B[qd])) (;W[qb];B[se] (;W[qd];B[sb]) (;W[ra]) (;W[sb])) (;W[qd];B[oa];W[qb];B[sb]) (;W[oa];B[se] (;W[qd]C[White is dead. Black can take all outside liberties, then give atari at S19. If White plays T19, S19 or R18 White plays T18 to create a 4 stone nakade shape. T19 then T18 etc.]) (;W[sb]) (;W[ra];B[qd]) (;W[qb];B[qd]))) (;W[sc];B[sb] (;W[sd];B[se] (;W[qd];B[ra]MA[rb]C[If White captures the Black stones Black will play S18 to reduce the corner group to one eye.]) (;W[oa];B[qd]) (;W[ra];B[qd])) (;W[oa];B[sd])) (;W[oa];B[sd]) (;W[ra];B[sd]) (;W[qb];B[sd])) (;W[rc];B[qa]) (;W[qb];B[qa]) (;W[sd];B[qa]) (;W[sc];B[qa]) (;W[oa];B[qa])) (;W[rc];B[ra] (;W[qb];B[qa]) (;W[qa];B[qb] (;W[qc];B[rb]) (;W[rb];B[qa])) (;W[rb];B[qa])) (;W[ra];B[rc] (;W[qc];B[sd] (;W[rb];B[sc]) (;W[qa];B[rb]) (;W[sb];B[sc])) (;W[rb];B[qc]) (;W[sd];B[qc])) (;W[sd];B[rb] (;W[qa];B[rc];W[qc];B[sc] (;W[ra];B[se] (;W[qd];B[sb]) (;W[sb];B[qd]) (;W[qb];B[qd])) (;W[sb];B[se] (;W[qd];B[sa]C[White is dead. Black can take all outside liberties, then give atari at S19. If White plays S19 or R18 White plays T18 to create a 5 stone nakade shape.]) (;W[ra]) (;W[qb];B[qd]) (;W[sa];B[qd]) (;W[oa];B[qd])) (;W[qb];B[se] (;W[qd];B[sb]) (;W[ra]) (;W[sb])) (;W[qd];B[oa];W[qb];B[sb]) (;W[oa];B[se] (;W[qd]C[White is dead. Black can take all outside liberties, then give atari at S19. If White plays T19, S19 or R18 White plays T18 to create a 4 stone nakade shape. T19 then T18 etc.]) (;W[sb]) (;W[ra];B[qd]) (;W[qb];B[qd]))) (;W[qb];B[qa]) (;W[qc];B[qb]) (;W[rc];B[qb]) (;W[oa];B[qa])) (;W[sc];B[rb] (;W[qa];B[rc] (;W[qc];B[sb] (;W[sd];B[se] (;W[qd];B[ra]MA[rb]C[If White captures the Black stones Black will play S18 to reduce the corner group to one eye.]) (;W[oa];B[qd]) (;W[ra];B[qd])) (;W[oa];B[sd])) (;W[sd];B[qc]) (;W[se];B[qc] (;W[sb];B[sf]) (;W[ra];B[sb]) (;W[qb];B[sb]))) (;W[rc];B[qa]) (;W[qb];B[qa]) (;W[qc];B[qb]) (;W[ra];B[qb]) (;W[sb];B[qb])) (;W[sb];B[rb] (;W[qa];B[rc] (;W[qc];B[sd]) (;W[sd];B[qc])) (;W[rc];B[qb]) (;W[qb];B[rc];W[qc] (;B[sd];W[ra];B[qd]) (;B[ra];W[qa];B[sd])) (;W[qc];B[qa]) (;W[sd];B[qb]) (;W[ra];B[qb])) (;W[oa];B[rc] (;W[qc];B[rb] (;W[sd];B[sc] (;W[sb];B[se] (;W[qd];B[sa]) (;W[ra];B[qd]) (;W[qb];B[qd])) (;W[ra];B[se] (;W[qb];B[qd]) (;W[qd];B[sb]) (;W[sb];B[qd]) (;W[qa];B[qd])) (;W[qb];B[se];W[qd];B[sb]) (;W[qa];B[se] (;W[qd]C[White is dead. Black can take all outside liberties, then give atari at S19. If White plays T19, S19 or R18 White plays T18 to create a 4 stone nakade shape. T19 then T18 etc.]) (;W[sb]) (;W[ra];B[qd]) (;W[qb];B[qd])) (;W[qd];B[qa])) (;W[qa];B[sd]) (;W[qd];B[sd]) (;W[sc];B[sb];W[sd];B[se];W[qd];B[ra])) (;W[sd];B[qc])))