A number is a palindrome if its digits are the same when written forward or backward. For example, the numbers $$7$$, $$11111$$ and $$302203$$ are palindromes. What is the smallest number that can be added to $$40309$$ to create a palindrome?~\uline{~~~~~~~~~~}~ 
Overseas Competition->Knowledge Point->Number Theory Modules->Place Value and Number Bases->Applying the Principle of Place Value