Longest Balanced Substring

You are given a string s consisting solely of the characters 'x' and 'y'. A substring of s is considered balanced if it contains an equal number of 'x' and 'y'. Your task is to determine the length of the longest balanced substring within s.

More formally, let S be a string of length n such that S[i] \in \{'x', 'y'\} for all 0 \le i < n. Find the maximum length L such that there exists indices i and j (with i < j) for which the substring S[i...j] is balanced, i.e., \[ \#\{ k | S[k] = 'x',\, i \leq k \leq j \} = \#\{ k | S[k] = 'y',\, i \leq k \leq j \}. \] If no such substring exists, output 0.

Example:

• Input: xyxyxxxyy → Output: 8
• Input: xxyyy → Output: 4
• Input: xxx → Output: 0

inputFormat

The input consists of a single line containing a non-empty string s comprised only of the characters 'x' and 'y'.

outputFormat

Output a single integer representing the length of the longest balanced substring found in s. If no balanced substring exists, output 0.

xyxyxxxyy

8