Problems
Palindrome
Palindrome
Given string. In one operation you can swap any two letters. Find minimum number of operations needed in order to receive palindrome or -1 if it is impossible.
Input
First line contains one string s (1 ≤ |s| ≤ 1000). Given string is not empty and only contains small latin letters.
Output
Print the minimum number of operations needed in order to receive palindrome or -1 if it is impossible.
Input example #1
abab
Output example #1
1
Input example #2
abc
Output example #2
-1