Six friends T, M, N, S, A and B are living in six floor building but not necessarily in the same order, numbered from the bottom as 1 to top as 6.  M is living at an even numbered floor. T is living above M and N. B is living below S. There are two floors between M and A, who is not living at the bottom. There is one person gap between M and N. At which floor S is living?