First Non-Repeating Character

You are given a string s. Your task is to find the first character in s that does not repeat anywhere in the string. If every character in the string repeats, output an empty string.

The idea is to scan through the string and determine the frequency of each character. Formally, for a string \( s \) of length \( n \), define the frequency function \( f(c) \) as:

[ f(c) = #{ i \mid 0 \le i < n \text{ and } s[i] = c }]

Your task is to find the smallest index \( i \) such that \( f(s[i]) = 1 \) and print \( s[i] \). If no such index exists, print nothing (i.e., an empty string).

inputFormat

The input consists of a single line containing the string s.

Note: The string may be empty.

outputFormat

Print the first non-repeating character in the string s. If there is no such character, output an empty string.

swiss

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