Black has more ko threats than White. Find the best move.
(;AB[bp]AB[cp]AB[dp]AB[eq]AB[fr]AB[gr]AB[gq]AB[hp]AB[ho]AB[hn]AB[hm]AB[iq]AB[ir]AB[fl]AW[bo]AW[co]AW[do]AW[ep]AW[fq]AW[fp]AW[gp]AW[go]AW[gn]AW[fn]AW[en]AW[dm]AW[bl]C[Beware of ko...]AP[goproblems]
(;W[dq];B[er]
(;W[bq];B[cq]
(;W[cr];B[ap]
(;W[dr];B[br]
(;W[ar];B[aq]
(;W[bs];B[as]C[White now has to win a two stage ko.])
(;W[ao];B[as]))
(;W[ao];B[aq])
(;W[bs];B[ar]))
(;W[br];B[dr])
(;W[aq];B[dr])
(;W[ao];B[dr])
(;W[ar];B[dr])
(;W[bs];B[dr]))
(;W[ap];B[cr]C[White can squeeze Black even tighter than this.])
(;W[dr];B[aq])
(;W[br];B[ap])
(;W[aq];B[ap])
(;W[ao];B[ap])
(;W[ar];B[ap]))
(;W[cq];B[bq])
(;W[cr];B[cq]
(;W[dr];B[br])
(;W[ap]
(;B[dr]C[CHOICE]
(;W[bq]C[White squeezes the corner away from Black.RIGHT])
(;W[br];B[aq])
(;W[aq];B[br])
(;W[ar];B[br])
(;W[ao];B[aq])
(;W[ds];B[aq])
(;W[cs];B[aq])
(;W[bs];B[aq])
(;W[as];B[aq]))
(;B[bq]C[In the endgame this is the best way for Black to continue.CHOICE]
(;W[br];B[dr]
(;W[aq]C[];B[dq]C[This is what Black would play in the endgame. Next, C1 is a 5 point gote move for both.RIGHT]
(;W[cs]C[White has secured 4 points and can get a further point per move by playing D1, E1 etc. until Black drops the lid on that.RIGHT]MA[ar]MA[as]MA[bs]MA[ao]TR[ds])
(;W[ds];B[ar]
(;W[as];B[cs]
(;W[bs];B[es]
(;W[ao];B[cs];W[ar]C[No territory at all in the corner.])
(;W[ar];B[cs];W[ao]C[No territory at all in the corner.]))
(;W[ao];B[es])
(;W[ar];B[es]))
(;W[ao];B[bs]C[Ko])
(;W[cs];B[ao])
(;W[bs];B[ao])))
(;W[ar]MA[aq]MA[cs]C[White connects the stones, but this is gote and at least one point worse than wA3, bD3, wC1.]MA[dq])
(;W[as];B[aq])
(;W[bs];B[aq])
(;W[cs];B[aq])
(;W[ds];B[aq]))
(;W[aq];B[br]
(;W[ar];B[bs])
(;W[dr];B[ar]
(;W[ao];B[ds])
(;W[bs];B[ao])
(;W[as];B[ao])
(;W[cs];B[ao])
(;W[ds];B[ao]))
(;W[bs];B[dr]
(;W[ar];B[cs])
(;W[cs];B[ar])
(;W[as];B[cs])
(;W[ao];B[ar]))
(;W[ao];B[ar])
(;W[cs];B[ar]
(;W[dr];B[ao])
(;W[ao];B[dr])
(;W[bs];B[ao])
(;W[as];B[ao])))
(;W[dr];B[br]
(;W[aq];B[ar]
(;W[ao];B[ds])
(;W[bs];B[ao])
(;W[as];B[ao])
(;W[cs];B[ao])
(;W[ds];B[ao]))
(;W[ar];B[bs])
(;W[bs];B[ar]))
(;W[ar];B[br]
(;W[bs];B[dr]
(;W[cs];B[ds]
(;W[aq];B[as])
(;W[as];B[aq])
(;W[ao];B[as]))
(;W[aq];B[cs])
(;W[as];B[cs])
(;W[ao];B[cs])
(;W[ds];B[cs]C[A ko by which White has nothing to gain (Black can play E1 to end it); also Black has an internal ko threat at D3.]MA[es]MA[dq]))
(;W[aq];B[bs])
(;W[dr];B[bs])
(;W[ao];B[bs])
(;W[cs];B[bs])
(;W[as];B[bs]))))
(;W[br];B[dr]
(;W[ap];B[aq])
(;W[bq];B[ao])
(;W[aq];B[ap])
(;W[ar];B[ao])
(;W[ao];B[ap]))
(;W[bq];B[ap]
(;W[dr];B[br]
(;W[ar];B[aq]
(;W[bs];B[as]C[White now has to win a two stage ko.])
(;W[ao];B[as]))
(;W[ao];B[aq])
(;W[bs];B[ar]))
(;W[br];B[dr])
(;W[aq];B[dr])
(;W[ao];B[dr])
(;W[ar];B[dr])
(;W[bs];B[dr]))
(;W[aq];B[ap]
(;W[dr];B[br]
(;W[ao];B[bq];W[bs];B[ar])
(;W[bq];B[ar])
(;W[ar];B[cs])
(;W[bs];B[ds])
(;W[cs];B[bs])
(;W[ds];B[es]))
(;W[bq];B[dr])
(;W[ao];B[dr])
(;W[br];B[dr]))
(;W[ao];B[ap]
(;W[dr];B[br]
(;W[aq];B[bq];W[bs];B[ar])
(;W[bq];B[aq])
(;W[ar];B[cs])
(;W[bs];B[ds]))
(;W[br];B[dr])
(;W[aq];B[dr])
(;W[bq];B[dr]))
(;W[ar];B[aq]
(;W[dr];B[br]
(;W[bs];B[as]C[Two-stage ko.])
(;W[ap];B[ao];W[bs];B[as]C[Two stage ko, and White just wasted a ko threat.])
(;W[ao];B[cs]))
(;W[br];B[dr])
(;W[ap];B[ao]
(;W[dr];B[br];W[bs];B[as]C[Two stage ko, and White just wasted a ko threat.])
(;W[br];B[dr])
(;W[bq];B[br])
(;W[an];B[dr]))
(;W[bq];B[br]))
(;W[bs];B[dr])
(;W[cs];B[dr]))
(;W[dr];B[br]C[Nice solid corner.])
(;W[br];B[cq])
(;W[ap];B[cr]
(;W[br];B[cq]C[Nice, but you can squeeze Black even tighter.])
(;W[bq];B[cq]C[Nice, but you can squeeze Black even tighter.])
(;W[cq];B[bq]
(;W[br];B[dr];W[aq]C[Not good enough.])
(;W[aq];B[br])
(;W[ar];B[br]))
(;W[aq];B[br])
(;W[ar];B[br])
(;W[bs];B[bq])
(;W[dr];B[br]))
(;W[aq];B[br])
(;W[ar];B[br]
(;W[cr];B[bq])
(;W[dr];B[cr])
(;W[bq];B[cq])
(;W[cq];B[bq])
(;W[ap];B[bq])
(;W[aq];B[ap])
(;W[bs];B[aq]
(;W[cr];B[as]C[Don't bother to find a ko threat; ko would be a success for Black.]
(;W[cs];B[cq]
(;W[ao];B[ap])
(;W[ap];B[ao])
(;W[ar];B[dr]))
(;W[bq];B[cs])
(;W[dr];B[ar];W[cq])
(;W[cq];B[cs])
(;W[ao];B[cs])
(;W[ap];B[cs])
(;W[ar]C[NOTTHIS]))
(;W[cq];B[cr])
(;W[dr];B[cs])
(;W[cs];B[cq])
(;W[ao];B[cs])
(;W[ds];B[dr]))
(;W[cs];B[aq]))
(;W[bs];B[cq])
(;W[cs];B[cq])
(;W[ds];B[cq])
(;W[as];B[ap])
(;W[ao];B[cq]))
(;W[er];B[dq])
(;W[dr];B[dq]
(;W[ap];B[aq])
(;W[er];B[cr])
(;W[cr];B[er])
(;W[cq];B[er])
(;W[bq];B[ap]))
(;W[bq];B[cq]
(;W[cr];B[br]
(;W[dr];B[er]
(;W[dq];B[aq])
(;W[bs]
(;B[aq])
(;B[ar]
(;W[dq];B[aq])
(;W[ap];B[dq])))
(;W[aq];B[ap]))
(;W[er];B[dq]
(;W[dr];B[aq]
(;W[ao])
(;W[bs];B[ar]
(;W[ao];B[ap];W[cs];B[es])
(;W[cs];B[es])
(;W[es];B[cs])))
(;W[ap];B[aq];W[dr];B[ao]))
(;W[ap];B[aq];W[er];B[dq];W[dr];B[ao]))
(;W[dr];B[br]
(;W[er];B[dq];W[cr];B[aq]
(;W[ao])
(;W[bs];B[ar]
(;W[ao];B[ap];W[cs];B[es])
(;W[cs];B[es])
(;W[es];B[cs])))
(;W[dq];B[er]
(;W[ap];B[aq]
(;W[cr];B[ao])
(;W[ao];B[cr]))
(;W[cr];B[aq]))
(;W[cr];B[er]
(;W[dq];B[aq])
(;W[bs]
(;B[aq])
(;B[ar]
(;W[dq];B[aq])
(;W[ap];B[dq])))
(;W[aq];B[ap]))
(;W[ap];B[aq];W[er];B[dq];W[cr];B[ao])
(;W[aq];B[ap]
(;W[er];B[dq];W[cr];B[ar])
(;W[dq];B[er];W[cr];B[ar])))
(;W[ap];B[br]
(;W[aq];B[ar]
(;W[er];B[dq]
(;W[cr];B[ao])
(;W[ao];B[dr]))
(;W[cr];B[ao])
(;W[dr];B[er]))
(;W[er];B[dq];W[cr];B[aq];W[dr];B[ao]))
(;W[er];B[dq]
(;W[ap];B[br];W[cr])
(;W[cr];B[br]
(;W[dr];B[aq]
(;W[ao])
(;W[bs];B[ar]
(;W[ao];B[ap];W[cs];B[es])
(;W[cs];B[es])
(;W[es];B[cs])))
(;W[ap];B[aq];W[dr];B[ao]))
(;W[dr];B[br];W[cr])))
(;W[cq];B[dq])
(;W[cr];B[dr])
(;W[br];B[dr])
(;W[ap];B[cq]
(;W[bq];B[br]
(;W[aq];B[ar]
(;W[er];B[dq]
(;W[cr];B[ao])
(;W[ao];B[dr]))
(;W[cr];B[ao])
(;W[dr];B[er]))
(;W[er];B[dq];W[cr]))
(;W[dr];B[er]
(;W[bq];B[br]
(;W[cr];B[aq]
(;W[dq];B[ao])
(;W[ao];B[dq]))
(;W[dq];B[aq]
(;W[cr];B[ao])
(;W[ao];B[cr]))
(;W[aq];B[ar])
(;W[ar];B[aq]MA[cr]C[Black can either fight the ko or connect.];W[dq];B[ao])
(;W[bs];B[aq])
(;W[ao];B[aq]))
(;W[cr];B[br]
(;W[bq];B[aq]
(;W[dq])
(;W[ao];B[dq]))
(;W[aq];B[ar]
(;W[dq];B[bq]
(;W[ao];B[ds])
(;W[bs];B[ao])
(;W[as];B[ao])
(;W[cs];B[ao])
(;W[ds];B[ao]))
(;W[ao];B[bq])
(;W[bs];B[dq]))
(;W[ar];B[bs]
(;W[dq];B[bq])
(;W[bq];B[aq]C[If Black cannot win the ko the connection at A is good enough.
If White plays B instead of the ko then Black connects the ko; White A does not work..]LB[ao:B]LB[dq:A])
(;W[aq];B[bq]))
(;W[bs]
(;B[aq])
(;B[ar]
(;W[dq];B[bq])
(;W[bq];B[dq])
(;W[aq];B[dq])))
(;W[dq];B[bq]
(;W[aq])
(;W[ar];B[bs])
(;W[bs];B[ar])))
(;W[br];B[aq])
(;W[aq];B[br]
(;W[bq];B[ar])
(;W[ar];B[bs])
(;W[cr];B[ar]
(;W[dq];B[bq])
(;W[ao];B[bq])
(;W[bs];B[dq]))
(;W[dq];B[ar])
(;W[cs];B[ar])
(;W[ds];B[ar])
(;W[bs];B[ar]))
(;W[ar];B[br]
(;W[cr];B[bs]
(;W[dq];B[bq])
(;W[bq];B[aq]C[If Black cannot win the ko the connection at A is good enough.
If White plays B instead of the ko then Black connects the ko; White A does not work..]LB[ao:B]LB[dq:A])
(;W[aq];B[bq]))
(;W[bs];B[cs])
(;W[bq];B[aq]MA[cr]C[Black can either fight the ko or connect.];W[dq];B[ao])
(;W[dq];B[ds])
(;W[aq];B[bs])
(;W[cs];B[bs])
(;W[ds];B[bs]))
(;W[dq];B[cr])
(;W[cs];B[aq])
(;W[ds];B[aq])
(;W[bs];B[aq]))
(;W[er];B[dr]
(;W[dq];B[aq]
(;W[eq];B[br])
(;W[es];B[eq]C[Ko])
(;W[cr];B[eq]C[Ko])
(;W[ao];B[es])
(;W[ds];B[eq]C[Ko])
(;W[br];B[es]))
(;W[bq];B[br];W[dq];B[aq])
(;W[br];B[aq]
(;W[dq];B[es])
(;W[es];B[dq])
(;W[ao];B[bq]
(;W[dq];B[es])
(;W[es];B[dq]))
(;W[cr];B[es])
(;W[bq];B[ao]
(;W[dq];B[es])
(;W[es];B[dq])
(;W[an];B[ap]
(;W[dq];B[es])
(;W[es];B[dq])
(;W[cr];B[es]))))
(;W[es];B[dq]MA[aq]C[Instead of connecting at D3 Black might well allow the ko fight by playing A3.])
(;W[aq];B[br]
(;W[dq];B[es])
(;W[es];B[dq])
(;W[ar];B[es])
(;W[bq];B[ar]))
(;W[ar];B[br]
(;W[dq];B[es])
(;W[es];B[dq])
(;W[bs];B[cs]
(;W[es];B[dq])
(;W[dq];B[as]
(;W[es];B[aq])
(;W[eq];B[aq])
(;W[aq];B[es])
(;W[ds];B[es]
(;W[bs];B[eq])
(;W[aq];B[eq])))
(;W[aq];B[es])
(;W[bq];B[as]TR[ar]TR[bq]C[The marked stones are captured with double ko.]))
(;W[aq];B[es]))
(;W[cr];B[br]
(;W[dq];B[cs]
(;W[es];B[aq])
(;W[eq];B[es])
(;W[aq];B[es]))
(;W[cs];B[es])
(;W[es];B[aq]
(;W[dq];B[cs])
(;W[cs];B[bs])
(;W[ds];B[cs])))
(;W[cs];B[aq]
(;W[es];B[dq]
(;W[ds];B[br]
(;W[cr];B[ao])
(;W[bs];B[ar]
(;W[cr];B[ao])
(;W[ao];B[fs]))
(;W[ar];B[ao]
(;W[an];B[bs])
(;W[cr];B[bs])
(;W[bs];B[cr]))
(;W[ao];B[bs]))
(;W[br];B[ds])
(;W[ao];B[ds])
(;W[ar];B[ao]
(;W[ds];B[bs]
(;W[br];B[cr])
(;W[cr];B[br])
(;W[an];B[br]))
(;W[br];B[ds])
(;W[an];B[ds])))
(;W[ao];B[es])
(;W[dq];B[es])
(;W[cr];B[es])
(;W[ds];B[es])
(;W[br];B[es]))
(;W[bs];B[aq]
(;W[dq];B[es])
(;W[es];B[dq]
(;W[ds];B[fs];W[cs];B[br])
(;W[ar];B[ao]
(;W[ds];B[fs];W[cs];B[br])
(;W[br];B[ds])
(;W[cr];B[ds])
(;W[cs];B[ds])
(;W[an];B[ds]))
(;W[ao];B[ds])
(;W[br];B[ds]))
(;W[ao];B[es]))
(;W[ds];B[es]MA[aq]C[Instead of capturing at E1 Black could also allow the ko fight by playing A3]))
(;W[br];B[aq]
(;W[er];B[dr]
(;W[dq];B[es])
(;W[es];B[dq])
(;W[ao];B[bq]
(;W[dq];B[es])
(;W[es];B[dq]))
(;W[cr];B[es])
(;W[bq];B[ao]
(;W[dq];B[es])
(;W[es];B[dq])
(;W[an];B[ap]
(;W[dq];B[es])
(;W[es];B[dq])
(;W[cr];B[es]))))
(;W[dr];B[er])
(;W[cr];B[dr])
(;W[bq];B[ao]
(;W[dr];B[er])
(;W[er];B[dr]
(;W[dq];B[es])
(;W[es];B[dq])
(;W[an];B[ap]
(;W[dq];B[es])
(;W[es];B[dq])
(;W[cr];B[es])))
(;W[cr];B[dr])
(;W[ar];B[ap]
(;W[dr];B[er])
(;W[er];B[dr]
(;W[es];B[dq])
(;W[an];B[es])
(;W[cr];B[es])
(;W[dq];B[es]))
(;W[cr];B[dr])
(;W[an];B[dr])))
(;W[ar];B[ao]
(;W[dr];B[er])
(;W[er];B[dr])
(;W[cr];B[dr])
(;W[an];B[ap]
(;W[dr];B[er])
(;W[cr];B[dr])
(;W[er];B[dr]
(;W[dq];B[es])
(;W[es];B[dq])
(;W[cr];B[es])))
(;W[bq];B[ap]
(;W[dr];B[er])
(;W[er];B[dr]
(;W[es];B[dq])
(;W[an];B[es])
(;W[cr];B[es])
(;W[dq];B[es]))
(;W[cr];B[dr])
(;W[an];B[dr]))))
(;W[cr];B[br]
(;W[er];B[dr]
(;W[dq];B[cs]
(;W[es];B[aq])
(;W[eq];B[es])
(;W[aq];B[es]))
(;W[cs];B[es])
(;W[es];B[aq]
(;W[dq];B[cs])
(;W[cs];B[bs])
(;W[ds];B[cs])))
(;W[dr];B[er]
(;W[bq])
(;W[aq];B[ar]
(;W[dq];B[bq])
(;W[ao];B[bq])
(;W[bs];B[dq]))
(;W[ar];B[bs]
(;W[dq];B[bq])
(;W[bq];B[aq]C[If Black cannot win the ko the connection at A is good enough.
If White plays B instead of the ko then Black connects the ko; White A does not work..]LB[ao:B]LB[dq:A])
(;W[aq];B[bq]))
(;W[bs]
(;B[aq])
(;B[ar]
(;W[dq];B[bq])
(;W[bq])
(;W[aq])))
(;W[dq];B[bq]))
(;W[ar];B[bs];W[er]
(;B[dq]
(;W[dr];B[bq])
(;W[bq];B[aq];W[dr];B[ao];W[an];B[bq]))
(;B[dr];W[dq];B[cs];W[es];B[eq]MA[aq]C[Black can also live in double ko by playing at A3.])))
(;W[aq];B[br]
(;W[er];B[dq])
(;W[dr];B[er]
(;W[bq])
(;W[ar];B[bs])
(;W[cr];B[ar])
(;W[dq];B[ar])
(;W[cs];B[ar])
(;W[ds];B[ar])
(;W[bs];B[ar]))
(;W[cr];B[dr])
(;W[ar];B[bs]
(;W[er];B[dq])
(;W[bq];B[dr])
(;W[dr];B[er]))
(;W[bq];B[ar]
(;W[er];B[dq]
(;W[cr];B[ao])
(;W[ao];B[dr]))
(;W[cr];B[ao])
(;W[dr];B[er])))
(;W[ar];B[br]
(;W[dr];B[er]
(;W[cr])
(;W[bs];B[cs])
(;W[bq])
(;W[dq];B[ds])
(;W[aq])
(;W[cs];B[bs])
(;W[ds];B[bs]))
(;W[er];B[dr]
(;W[dq];B[es])
(;W[es];B[dq])
(;W[bs];B[cs]
(;W[es];B[dq])
(;W[dq];B[as]
(;W[es];B[aq])
(;W[eq];B[aq])
(;W[aq];B[es])
(;W[ds];B[es]
(;W[bs];B[eq])
(;W[aq];B[eq])))
(;W[aq];B[es])
(;W[bq];B[as]TR[ar]TR[bq]C[The marked stones are captured with double ko.]))
(;W[aq];B[es]))
(;W[cr];B[bs];W[er]
(;B[dq]
(;W[dr];B[bq])
(;W[bq];B[aq];W[dr];B[ao];W[an];B[bq]))
(;B[dr];W[dq];B[cs];W[es];B[eq]MA[aq]C[Black can also live in double ko by playing at A3.]))
(;W[bs];B[cs]
(;W[er];B[dr]
(;W[es];B[dq])
(;W[dq];B[as]
(;W[es];B[aq])
(;W[eq];B[aq])
(;W[aq];B[es])
(;W[ds];B[es]
(;W[bs];B[eq])
(;W[aq];B[eq])))
(;W[aq];B[es])
(;W[bq];B[as]TR[ar]TR[bq]C[The marked stones are captured with double ko.]))
(;W[dr];B[er])
(;W[bq];B[aq]C[Black lives with double ko])
(;W[aq];B[dr]))
(;W[bq];B[cr])
(;W[cs];B[bs]
(;W[dr];B[er])
(;W[er];B[dq])
(;W[cr];B[dr])))
(;W[cs];B[aq];W[er];B[dr]
(;W[es];B[dq]
(;W[ds];B[br]
(;W[cr];B[ao])
(;W[bs];B[ar]
(;W[cr];B[ao])
(;W[ao];B[fs]))
(;W[ar];B[ao]
(;W[an];B[bs])
(;W[cr];B[bs])
(;W[bs];B[cr]))
(;W[ao];B[bs]))
(;W[br];B[ds])
(;W[ao];B[ds])
(;W[ar];B[ao]
(;W[ds];B[bs]
(;W[br];B[cr])
(;W[cr];B[br])
(;W[an];B[br]))
(;W[br];B[ds])
(;W[an];B[ds])))
(;W[ao];B[es])
(;W[dq];B[es])
(;W[cr];B[es])
(;W[ds];B[es])
(;W[br];B[es]))
(;W[ds];B[aq]
(;W[er];B[dq])
(;W[dr];B[er])
(;W[br];B[dr])
(;W[cr];B[dr])
(;W[ar];B[ao];W[er];B[dq];W[cs];B[dr];W[es];B[bs]
(;W[br];B[cr])
(;W[cr];B[br])
(;W[an];B[br])))
(;W[bs];B[aq];W[er];B[dq];W[ds];B[dr];W[es];B[fs];W[cs];B[br])
(;W[ao];B[aq]
(;W[br];B[bq]
(;W[er];B[dr]
(;W[dq];B[es])
(;W[es];B[dq]))
(;W[dr];B[er]))
(;W[er];B[dr];W[dq];B[es])
(;W[dr];B[er])))
(;W[aq];B[dr])
(;W[ar];B[dr])
(;W[cs];B[dr])
(;W[bs];B[dr])
(;W[ds];B[dr])
(;W[es];B[dr])
(;W[ao];B[dr]
(;W[ap];B[br])
(;W[aq];B[ap])
(;W[bq];B[ap])
(;W[cq];B[bq])
(;W[ar];B[ap])
(;W[br];B[ap])
(;W[cr];B[ap]))
(;W[as];B[dr]))