If R is absent from the office for a day, R is stiff possible for a memorandum to be passed on that day all the way along a route from 

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."