Longest Balanced Parentheses Substring

You are given a string s consisting only of the characters '(' and ')'. Your task is to compute the length of the longest substring of s that forms a valid (balanced) parentheses sequence.

A balanced parentheses string is defined as one in which each opening bracket ( has a corresponding closing bracket ) and the pairs of parentheses are properly nested. For example, the string (()()) is balanced and has a length of 6, while the string (() is not completely balanced and the longest balanced substring is () with a length of 2.

The solution to this problem requires an efficient algorithm that can handle large inputs using a stack-based approach.

inputFormat

The input consists of a single line, which is the string s composed exclusively of the characters '(' and ')'.

outputFormat

Output a single integer, which is the length of the longest balanced parentheses substring found in s.

The result should be printed to stdout.

(()())

6