Minimum Operations to Palindrome

Given a string \( s \) consisting only of lowercase English letters, your task is to determine the minimum number of operations required to transform \( s \) into a palindrome. In one operation, you can replace any character in the string with any other character.

A string is a palindrome if it reads the same forward and backward. The number of operations needed is computed by counting the positions \( i \) (from \( 1 \) to \( \lfloor n/2 \rfloor \)) where the character at position \( i \) does not match the character at position \( n+1-i \). Formally, if \( n \) is the length of \( s \), then the minimum number of operations is given by:

\[ \text{operations} = \sum_{i=1}^{\lfloor n/2 \rfloor} \mathbf{1}_{\{s_i \neq s_{n+1-i}\}} \]

inputFormat

The input is provided on a single line from standard input (stdin) and consists of the string \( s \) containing only lowercase English letters. The string may be empty.

outputFormat

Output a single integer to standard output (stdout) which is the minimum number of operations required to transform \( s \) into a palindrome.

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