Problem Statement 
 A number is called a perfect power if it can be written in the form m^k, where m and k are positive integers, and k > 1.
Given two positive integers A and B, find the two perfect powers between A and B, inclusive, that are closest to each other, and return the absolute difference between them. If less than two perfect powers exist in the interval, return 1 instead. 

Definition 
 Class:  PerfectPowers  Method:  nearestCouple  Parameters:  long, long  Returns:  long  Method signature:  long nearestCouple(long A, long B)  (be sure your method is public) 




Notes 
  1 is a perfect power. 

Constraints 
  A will be between 1 and 10^18, inclusive. 
  B will be between A+1 and 10^18, inclusive. 

Examples 
0)  
  Returns: 3  1 and 4 are the first pair of perfect powers. 


1)  
  Returns: 1  8 and 9 are the closest pair of perfect powers. 


2)  
  Returns: 1  No pair of perfect powers is present in the interval. 


3)  
  Returns: 1  This is the largest possible range, and 8 and 9 are the closest pair of perfect powers. 


4)  
 