Longest Substring Without Repeating Characters

Given a string s, your task is to find the length of the longest substring of s that contains no repeating characters.

In other words, let \( s = s_1s_2\ldots s_n \). You are required to calculate the value of

\( \max_{1 \leq i \leq n} \{ j-i+1 \} \)

subject to the condition that the substring \( s_i s_{i+1} \ldots s_j \) contains only unique characters. For example, for the input "abcabcbb", the longest substring with all unique characters is "abc" with length 3.

This is a typical problem that can be solved efficiently using a sliding window approach.

inputFormat

A single string is provided via standard input (stdin). The string may be empty and can contain spaces or any printable characters.

outputFormat

Output a single integer to standard output (stdout) representing the length of the longest substring with all unique characters.## sample

abcabcbb

3