Read the following passage and solve the questions based on it.
Mr Manoj is a medical representative and he is supposed to visit six doctors—M, N, P, Q, R and S, exactly once every week. To visit the doctors, Mr Manoj has set up a schedule to visit each of the six doctors during the course of one week according to the following conditions:
(i) He must visit Dr M before Dr N and Dr R.
(ii) He must visit Dr N before Dr Q.
(iii) The third doctor he visits must be Dr P.
If he visits Dr S first, which doctor must he visit second?