Find the First Non-Repeating Character

Given a string ( s ), your task is to identify the first character that occurs exactly once. If every character in ( s ) repeats, output an empty string.

For example, if ( s = \texttt{swiss} ), then the first unique character is ( 'w' ) because the character 's' appears multiple times and 'w' is the first character that doesn't repeat.

inputFormat

The input consists of a single line containing the string ( s ). The string may include printable ASCII characters.

outputFormat

Output the first non-repeating character of the string ( s ). If no such character exists, output an empty string (i.e. nothing is printed).## sample

swiss

w