A memorandum can travel along two alternative route that have on employee is common except that writer and the final recipient if the write and the final recipient, respectively are 

In an office there are exactly seven employees - N, P, Q, R, S, T and U. An employee can pass along any memoranda written by that employee as well as any memoranda received from others, but only according to specific rule "Mumoranda can be passed in either dircetion between P and Q, is either direction between R and U, and is either direction between S and T. "Momoranda can be paused from N to S, from Q to R, from S to P, form U to N and from U to Q."