First Unique Character Index

You are given a single line containing a string s made of lowercase English letters. A character is unique if it appears exactly once in s.

Find the leftmost unique character and print its 0-based index. If no character is unique (or the string is empty), print -1.

Input format

A single line containing the string s. The line may be empty, in which case s is the empty string.

Output format

A single integer: the 0-based index of the first unique character, or -1 if there is no unique character.

Constraints

• 0 ≤ length of s ≤ 100000
• s consists only of lowercase English letters (a–z).