Longest Unique Substring

You are given a string S. Your task is to determine the length of the longest substring of S that contains no repeating characters. In other words, find the maximum length of a contiguous segment of characters where every character is unique.

For example, if S = "abcabcbb", the longest substring without repeating characters is "abc" which has a length of 3.

Note: If the string is empty, the answer should be 0.

You may assume that S consists of ASCII characters.

Mathematically, you need to compute:

\[ \max_{0 \leq i \leq j \leq |S|} \{ j-i \;:\; \forall k, l \in [i, j), \; S_k \neq S_l \text{ for } k \neq l \} \]

inputFormat

The input consists of a single string S provided through standard input (stdin). The string can contain letters, digits, and other ASCII symbols. It is guaranteed that the input does not contain leading or trailing spaces.

outputFormat

Output a single integer to standard output (stdout), which represents the length of the longest substring of S with all unique characters.

abcabcbb

3