209. Longest Substring with At Most Two Distinct Characters

Given a string s, return the length of the longest substring that contains at most two distinct characters.

Input: A single string s.

Output: An integer — the length of the longest valid substring.

Examples

Input: eceba
Output: 3
Explanation: The longest substring with at most 2 distinct chars is 'ece' (length 3).

Input: ccaabbb
Output: 5
Explanation: 'aabbb' has 2 distinct chars and length 5.

Input: abc
Output: 2
Explanation: 'ab' or 'bc' both have length 2.

Constraints

• 0 <= s.length <= 5×10^4
• s consists of English letters

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