First Non-Repeating Character

Given a string s, your task is to find the first non-repeating character in the string. A non-repeating character is one that appears only once in the string. If no such character exists, print an empty string.

For example, for the string abracadabra, the first non-repeating character is c because although some characters repeat, c appears only once and is the first such character in the order of appearance.

Mathematically, if we denote the input string as \( s = s_1s_2\ldots s_n \), the goal is to find the smallest index \( i \) such that \( \#(s_i) = 1 \), where \( \#(s_i) \) represents the frequency of the character \( s_i \) in \( s \).

inputFormat

The input is provided via standard input (stdin) and consists of a single line containing the string \( s \). The string may include letters, digits, symbols, or be empty.

Format: A single line containing the string.

outputFormat

The output should be written to standard output (stdout) and consist of a single line with the first non-repeating character found in the string. If there is no non-repeating character, output an empty string.

Format: A single line containing the result.

abracadabra

c