Longest Substring with At Most Two Distinct Characters

Given a string s, your task is to find the length of the longest substring that contains at most two distinct characters.

The substring must be contiguous. For example, when s = "eceba", the longest substring with at most two distinct characters is ece, so the answer is 3.

Note: If the input string is empty, the answer is 0.

Input and Output Format: The program reads the input from standard input (stdin) and prints the result to standard output (stdout).

inputFormat

A single line containing the string s.

outputFormat

An integer representing the length of the longest substring of s that contains at most two distinct characters.## sample

eceba

3