First Non-Repeating Character

Given a string, find the first non-repeating character. The input string will be provided on the first line, and the expected output will be the first non-repeating character, or a message indicating that no such character exists. If the input string is empty, the output should be an empty string. If the input string has only one character, the output should be that character. If the input string has multiple characters, the output should be the first character that appears only once in the string. The input string will only contain lowercase English letters.