Maximum Balanced Substring Length

Given a string s consisting only of letters 'a' and 'b', your task is to compute the maximum length of a balanced substring. A substring is considered balanced if it contains an equal number of 'a''s and 'b''s.

Note: A substring is a contiguous block of characters within the string.

Examples:

• For s = "aabb", the entire string is balanced, so the answer is 4.
• For s = "aaabb", the longest balanced substring is "aabb" with length 4.
• For s = "aaaa" or s = "bbbb", no balanced substring exists, so the answer is 0.

Your solution must read input from stdin and print the result to stdout.

inputFormat

The input consists of a single line containing a non-empty string s composed only of the characters 'a' and 'b'.

Examples:

aabb

outputFormat

Output a single integer representing the maximum length of a balanced substring within the given string.

Examples:

4

## sample

aaaa

0

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