This is equivalent to absorption to the left of the barrier c3 = — log^Fo/, in a one-dimensional random walk in which the particle starts at the origin and at each trial either moves left C2 = logA;(l —/) units with probability q or moves right ci = logA;(l+/) units with probability p. The formally different but similar problem where absorption occurs at the barrier, has a well-known solution in the event that C and C2 are integers,* and therefore in the event C and C2 are rationals.