First Non-Repeating Character

Given a string \(s\), your task is to find the first character that does not repeat in \(s\). Formally, find the first character \(c\) such that
\[ \text{count}(c)=1 \]
If no such character exists, output the underscore character '_'.

For example, if \(s = \texttt{aabbccdde}\), then the first non-repeating character is 'e' because all previous characters appear more than once.

inputFormat

The input consists of a single line containing the string \(s\). The string may contain any printable characters.

outputFormat

Output a single character — the first non-repeating character in \(s\). If there is no non-repeating character, output '_'.

a

a