Munaf and Surya start simultaneously at the same point on a circular track and run along the track in the same direction. The point on the track at which they meet for the $$31^{st}$$ time is the same as that at which they meet for the $$43^{rd}$$ time. If the ratio of the speed of the faster boy to that of the slower one is n : 1, where ‘n’ is a natural number, which of the following is NOT a possible value of ‘n’?