Palindrome#7445
Given a string. In one operation you can swap any two letters. Find minimum number of operations needed in order to receive palindrome or if it is impossible.
First line contains one string (1 \leq |s| \leq 1000). Given string is not empty and only contains small latin letters.
Print the minimum number of operations needed in order to receive palindrome or if it is impossible.
Example 1
Example 2