Longest run without a repeat

Problem

A keyboard logger records a string of characters. Find the length of the longest stretch in which no character appears twice.

Example 1

Input

abcabcbb

Output

abc has length 3.

Example 2

Input

bbbbb

Output

Try the problem first. Open one hint at a time.

Hint 1

Keep a window with no repeated characters and the last position of each character.

Hint 2

When a character repeats inside the window, move the left end just past its previous position.

Write your Python code, run it on the examples and submit it to hidden tests.