Longest Substring Without Repeating Characters

Given a string s, your task is to determine the length of the longest substring of s that contains only unique characters.

A substring is a contiguous sequence of characters within a string. In this problem, no character should appear more than once in the considered substring.

The problem can be formulated mathematically as follows:

Find the maximum k such that there exists an index i for which the substring s[i:i+k] has all distinct characters. That is, for any two indices j and l with i ≤ j < l < i+k, we have s[j] ≠ s[l].

inputFormat

The input consists of a single line containing the string s. The string may be empty.

Input is provided via standard input (stdin).

outputFormat

Output the length of the longest substring of s that contains only unique characters.

Output the result to standard output (stdout).

abcabcbb

3