Longest substring without repeats

Problem

A scanner reads a line of characters. Print the length of the longest run of neighbouring characters in which no character appears twice.

Example 1

Input

abcabcbb

Output

abc has length 3.

Example 2

Input

bbbbb

Output

Every run is one letter.

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

Hint 1

Keep a window of characters with no repeats, and slide its left end forward when a repeat appears.

Hint 2

Store the last position of each character in a dictionary to jump the left end past the earlier copy.

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