Longest Unique Substring

Given a string s, your task is to compute the length of the longest substring containing only unique characters. In other words, find the maximum length segment of s in which no characters appear more than once.

For example, if s = "abcabcbb", then the longest substring with all unique characters is "abc" whose length is 3.

The problem can be formally defined as follows:

Given a string \( s \), determine the maximum integer \( L \) such that there exists a substring \( s[i \dots j] \) (with \( j - i + 1 = L \)) where all characters are distinct.

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

inputFormat

The input consists of a single line containing the string s. The string may include spaces and special characters. It can also be empty.

Input Format:

s

outputFormat

Output the length (an integer) of the longest substring of unique characters found in the input string.

Output Format:

L

where L is the answer.

## sample

abcabcbb

3