It seems to be a really famous problem. However if you haven't seen it yet and don't know the solution, please do take your time to solve it. I got the solution together with the problem and deeply regret not having a chance to try and solve it.
(;AW[ab]AW[ca]AW[eb]AW[dc]AW[cd]AB[fb]AB[fa]AB[fc]AB[fd]AB[ee]AB[de]AB[ce]AB[bf]AB[ae]C[Black moves and kills white.]AP[goproblems]
(;B[db];W[cb]
(;B[bc];W[bd]
(;B[ad];W[bb]
(;B[ac];W[ea]
(;B[ec];W[da]
(;B[cc]C[O_O Wow! Incredible! Really well done! ^_^RIGHT])
(;B[dd];W[cc]C[O_O]))
(;B[cc];W[ec]C[O_O]))
(;B[dd];W[ac]C[O_O])
(;B[ec];W[ac]C[O_O])
(;B[ea];W[ac]C[O_O]))
(;B[bb];W[ac]C[White lives...]TR[ba]TR[ea])
(;B[ac];W[ad]C[White lives...])
(;B[ea];W[bb]C[White lives...])
(;B[ec];W[bb]C[White lives...])
(;B[ba];W[bb]C[White lives...]))
(;B[bd];W[bc]C[White lives...])
(;B[ad];W[bc]C[White lives...])
(;B[ea];W[bc]C[White lives...])
(;B[bb];W[bc]C[White lives...])
(;B[ec];W[bc]C[White lives...]))
(;B[ea];W[bc]
(;B[cb];W[db]
(;B[ba];W[da];B[bb];W[ad];B[bd];W[be]MA[bd]C[A ko just can't be enough where an unconditional kill is possible.])
(;B[bb];W[ba]C[White lives...])
(;B[da];W[ba]C[White lives...])
(;B[ad];W[ba]C[White lives...]))
(;B[da];W[cb]C[White lives...])
(;B[ba];W[cb]C[White lives...])
(;B[db];W[cb]C[White lives...]))
(;B[da];W[ea]C[White lives...])
(;B[cb];W[bb]
(;B[da];W[ea]
(;B[ba];W[bd]C[]
(;B[cc];W[db];B[dd];W[ca]MA[da]C[A ko just can't be enough where an unconditional kill is possible.])
(;B[ad];W[db]C[Leads to an impossible ko. (3 wins to kill)])
(;B[ec];W[db]C[White lives...])
(;B[db];W[ec]C[White lives...])
(;B[ca];W[db]C[White lives...]))
(;B[bc];W[bd]
(;B[ba];W[ac]C[White lives...])
(;B[ad];W[ac]C[White lives...])))
(;B[ea];W[cc]C[White lives...])
(;B[db];W[cc]C[White lives...])
(;B[cc];W[bc]C[White lives...])
(;B[bc];W[cc]C[White lives... (Sure B16 lets live bigger but this is clearer..;)])
(;B[bd];W[cc]C[White lives...]))
(;B[ec];W[db]C[White lives...])
(;B[dd];W[bc]
(;B[cb];W[bb]C[White lives...])
(;B[ba];W[bb]C[White lives...])
(;B[bb];W[ba]C[White lives...])
(;B[da];W[cb]C[White lives...])
(;B[db];W[cb]C[White lives...])
(;B[ea];W[db]C[White lives...]))
(;B[cc];W[bc]
(;B[ea];W[db]C[White lives...])
(;B[db];W[cb]C[White lives...])
(;B[cb];W[db]C[White lives...])
(;B[da];W[ea]C[White lives...]))
(;B[bd];W[bc]
(;B[cb];W[ba]C[White lives...])
(;B[ea];W[cb]C[White lives...])
(;B[da];W[cb]C[White lives...])
(;B[db];W[cb]C[White lives...])
(;B[bb];W[cb]C[White lives...])
(;B[ba];W[cb]C[White lives...]))
(;B[bc];W[bb]
(;B[bd];W[cc]C[White lives...])
(;B[cc];W[bd]C[White lives...])
(;B[ad];W[cc]C[White lives...]))
(;B[bb];W[bc]
(;B[cb];W[db]
(;B[ba];W[ea];B[da]MA[ca]C[A ko just can't be enough where an unconditional kill is possible. (Even if it's a ko with approach.)])
(;B[ea];W[ba]C[White lives...]))
(;B[ba];W[cb]C[White lives...])
(;B[ea];W[cb]C[White lives...])
(;B[db];W[cb]C[White lives...])
(;B[da];W[cb]C[White lives...]))
(;B[ba];W[cb]
(;B[bc];W[bb]
(;B[bd];W[ea]C[White lives...])
(;B[ea];W[bd]
(;B[ad];W[ac]C[White lives...])
(;B[ac];W[ad]C[White lives...]))
(;B[ad];W[ea]C[White lives...]))
(;B[bd];W[bc]C[White lives...])
(;B[ea];W[bc]C[White lives...])
(;B[da];W[bc]C[White lives...]))
(;B[ad];W[bb]C[White lives...])
(;B[ac];W[bb]C[White lives...]))