This occurred in a private game. Black did not see the way to solve and white lived. There are several paths to ko, but only one correct first move.
(;AB[fq]AB[fp]AW[eq]AW[ep]AB[dq]AB[dr]AB[er]AW[dp]AW[co]AW[cn]AW[cm]AB[bp]AB[cp]AW[bq]AW[cq]AW[cr]AW[bs]AW[ds]AB[fs]AB[gs]AW[eo]AW[en]C[Black to do what he can. Please don't play useless moves.]AB[bo]AB[bn]AW[bm]AB[ar]AP[goproblems]
(;B[aq]C[]
(;W[as]
(;B[ap];W[an];B[es]C[];W[am];B[cs]C[Ko, white must find the first threat.RIGHT])
(;B[es]C[]
(;W[an]
(;B[cs]C[Ko, white must find the first threat.RIGHT])
(;B[ap];W[am];B[cs]C[Ko, white must find the first threat.RIGHT]))
(;W[ap]
(;B[ao];W[am];B[cs]C[Ko, White must find the first threat.RIGHT])
(;B[cs];W[br];B[aq];W[ds];B[ao];W[am]
(;B[cs]C[Ko, white must find the first threat.RIGHT])
(;B[ar]C[];W[ap];B[aq];W[an]))))
(;B[an];W[ap]
(;B[ao];W[am]C[White is alive. White may also tenuki and leave a ko threat for black.])
(;B[es];W[am]))
(;B[ao];W[am];B[es];W[an]C[White is alive. White may also tenuki and leave a ko threat for black.]))
(;W[ap]
(;B[ao]
(;W[as];B[es];W[am];B[cs]C[Ko, white must find the first threat.RIGHT])
(;W[am]C[If White tries to approach from the top...];B[br];W[cs];B[es]C[Black wins outright. White cannot play like this.RIGHT]))
(;B[es];W[an]TR[bn]TR[bo]TR[bp]TR[cp]C[Whtie is alive.]))
(;W[an];B[br];W[cs];B[es]C[RIGHT])
(;W[br];B[ap];W[an];B[es];W[am];B[cs]C[RIGHT]))
(;B[es];W[ap]
(;B[aq];W[an]TR[bn]TR[bo]TR[bp]TR[cp]C[Whtie is alive.])
(;B[cs];W[an]C[White is alive.]TR[bn]TR[bo]TR[bp]TR[cp])
(;B[br];W[cs]C[White is alive, black cannot push.])
(;B[as];W[aq];B[cs];W[br]C[White is alive, black cannot push.]TR[bn]TR[bo]TR[bp]TR[cp])
(;B[an];W[cs]
(;B[aq];W[am]C[White is alive.])
(;B[br];W[am]C[White is alive. White may also tenuki and leave a ko threat for black.])))
(;B[ao];W[am]C[];B[aq];W[an];B[ap];W[as]C[White is alive. White may also tenuki and leave a ko threat for black.])
(;B[an];W[am]C[White is alive.]TR[an]TR[bn]TR[bo]TR[bp]TR[cp])
(;B[ap];W[aq];B[br];W[as]C[White is alive.])
(;B[br];W[ap];B[es];W[cs]C[White is alive, black cannot push.])
(;B[as];W[ap]C[White is alive.]TR[bn]TR[bo]TR[bp]TR[cp]))