Problem Statement 
 A string composed of a's and b's is either redundant or nonredundant. A string is redundant if and only if it can be expressed as a shorter string replicated multiple times. For example, the string "ababab" is redundant since it is 3 copies of "ab" concatenated together. The string "ab" is called a root of "ababab". The string "aaaa" has 2 roots: "aa" and "a". A nice result in formal languages states that every redundant string has exactly 1 nonredundant root (it may have many redundant roots).
Only considering strings composed of a's and b's, return the number of redundant strings that have the given length. 

Definition 
 Class:  RedundantStrings  Method:  howMany  Parameters:  int  Returns:  int  Method signature:  int howMany(int length)  (be sure your method is public) 




Constraints 
  length will be between 1 and 60 inclusive. 

Examples 
0)  
  Returns: 0  There are no redundant strings of length 1. 


1)  
  Returns: 2  Both "aa" and "bb" are redundant. 


2)  
  Returns: 4  Here the redundant strings are "aaaa", "bbbb", "abab", and "baba". 


3)  
 
4)  
 