Takahashi loves palindromes. Non-palindromic strings are unacceptable to him. Each time he hugs a string, he can change one of its characters to any character of his choice.
Given is a string S. Find the minimum number of hugs needed to make S palindromic.

-----Constraints-----
- S is a string consisting of lowercase English letters.
- The length of S is between 1 and 100 (inclusive).

-----Input-----
Input is given from Standard Input in the following format:
S

-----Output-----
Print the minimum number of hugs needed to make S palindromic.

-----Sample Input-----
redcoder

-----Sample Output-----
1

For example, we can change the fourth character to o and get a palindrome redooder.

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