Minimum Changes to Palindrome

Given a string s, your task is to determine the minimum number of character changes required to transform s into a palindrome. A palindrome is a string that reads the same forwards and backwards.

You can change any character into any other character. The minimum number of changes required is given by the formula:

\( \text{minChanges} = \sum_{i=0}^{\lfloor \frac{n-1}{2} \rfloor} \mathbf{1}_{\{s[i] \neq s[n-i-1]\}} \)

where \( n \) is the length of the string and \( \mathbf{1}_{\{condition\}} \) is 1 if the condition is true and 0 otherwise.

inputFormat

The input consists of a single line containing the string s. The string contains only lowercase letters and its length can be up to \(10^5\).

outputFormat

Output a single integer which is the minimum number of changes required to convert the string into a palindrome.

## sample

race

2

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