Problem Statement
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 SS. Find the minimum number of hugs needed to make SS palindromic.
Constraints
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SS is a string consisting of lowercase English letters.
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The length of SS is between 11 and 100100 (inclusive).
Input
Input is given from Standard Input in the following format:
SS
Output
Print the minimum number of hugs needed to make SS palindromic.