Making a Palindrome with Minimum Cost

You are given a string s consisting of lowercase English letters. Your task is to compute the minimum total cost required to convert the string into a palindrome.

A string is a palindrome if it reads the same backward as forward. In this problem, you can change the characters to make the string palindromic. For each pair of characters at positions i and n-i-1 (where n is the length of the string and 0 \le i < n/2), if they are different, you incur a cost equal to the absolute difference of their ASCII values. Formally, the total cost is given by:

[ \text{Cost} = \sum_{i=0}^{\lfloor \frac{n}{2} \rfloor - 1} \left|\text{ord}(s[i]) - \text{ord}(s[n-i-1])\right| ]

Your goal is to compute and output this total cost.

Examples:

• For s = "abc", the cost is |ord('a')-ord('c')| = |97-99| = 2.
• For s = "abcd", the cost is |ord('a')-ord('d')| + |ord('b')-ord('c')| = |97-100| + |98-99| = 3 + 1 = 4.
• For s = "racecar", the string is already a palindrome so the cost is 0.

inputFormat

The input consists of a single line containing a non-empty string s of lowercase English letters.

outputFormat

Output a single integer — the minimum total cost required to convert the given string into a palindrome.

## sample

abc

2

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