First Non-Repeating Character

You are given a string (s). Your task is to find the first character in the string that does not repeat. If every character in the string repeats or the string is empty, output (\texttt{None}). This problem tests your ability to analyze the frequency of characters in a string and handle edge cases appropriately.

inputFormat

The input consists of a single line containing the string (s). The string may include spaces, digits, punctuation, or other special characters.

outputFormat

Output a single line containing the first non-repeating character from the string (s). If no such character exists, output (\texttt{None}).## sample

swiss

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