Longest unique stretch

Problem

Given a string of lowercase letters, find the length of the longest stretch of consecutive characters in which no letter repeats.

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 start and a dictionary of the last position of each letter.

Hint 2

When a letter repeats inside the window, move the start just after its last position.

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