next Smaller
[ASSIGNMENT]:

  Next smaller number with 
  the same digits
 TASK:
Write a function that takes a positive 
integer and returns the next smaller 
positive integer containing the same digits.

 Input >> Output Examples::
  nextSmaller(21) --> return 12
 nextSmaller(531) --> return 513
 nextSmaller(2071) --> return 2017  

Return -1, when there is no smaller number 
that contains the same digits. 

Also return -1 when the next smaller number 
with the same digits would require the 
leading digit to be zero.

  nextSmaller(9) --> return -1
 nextSmaller(111) --> return -1
 nextSmaller(135) --> return -1
 nextSmaller(1027) --> return -1 // 0721 is out since we don't write numbers with leading zeros   
 NOTE:
- Some tests will include very large numbers!
- Test data only employs positive integers!

  BONUS!
The function you write for this assignment
is the inverse of this task: "Next bigger
number with the same digits."



    HappyCodings!:) by @boolean maybe
Next smaller number with the same digits
