regex - Regular expression with decimal and character -

I am trying to write a regular expression that will accept the following:

  S # # # # # # # # #   
 Where # can be an integer of any size (in fact, decimal or beforehand decimal) I do not accept anything except If so, then there is something like this:  
  Like #. Will not be accepted because the first one of A is # # X will not be accepted because after decimal is x   
 will always have to start either one or a f, then a Number, a period, and second number all those parts are required and the numbers can be integer in any size and any number.   
 
 
 This regular expression:  
  / ^ [sf] \ d + \. \ D + $ /   
  Explanation   
 
  ^  is the one that matches the beginning of the string Have an account.  
  [sf]  another and it means  s  or  f .  
  \ d  means a digit.  
  +  means one or more.  
 .  matches a literal point.  
  $  is an anchor that matches the end of the string.