(;AW[rb]AW[qb]AW[qc]AB[qd]AB[rd]AB[rc]AB[qf]AW[pd]AW[od]AW[nd]AW[nc]AB[nb]AB[oc]AB[pc]AB[pb]AW[mb]AW[lc]AP[goproblems]
(;B[pa]
(;W[na]
(;B[sb];W[ob]
(;B[ra]C[RIGHT])
(;B[qa]C[RIGHT]))
(;B[ra];W[ob]
(;B[sb]C[RIGHT])
(;B[qa]C[RIGHT]))
(;B[ob];W[qa])
(;B[oa];W[ob])
(;B[qa];W[ob]
(;B[sb]C[RIGHT])
(;B[ra]C[RIGHT])))
(;W[oa]C[CHOICE]
(;B[ra]C[RIGHT])
(;B[qa];W[ra])
(;B[sb]C[RIGHT])))
(;B[oa];W[ra];B[sb];W[ma]C[:( White will start a ko next.])
(;B[sb];W[pa])
(;B[ra];W[pa])
(;B[qa];W[ra]
(;B[sb];W[pa])
(;B[pa];W[oa]))
(;B[na];W[pa]))