Write a function that returns the closest palindrome number to an integer. If two palindrome numbers tie in absolute distance, return the smaller number.
closestPalindrome(887) ➞ 888
closestPalindrome(100) ➞ 99
// 99 and 101 are equally distant, so we return the smaller palindrome.
closestPalindrome(888) ➞ 888
closestPalindrome(27) ➞ 22
If the number itself is a palindrome, return that number.