First Non-Repeated Character

You are given a string S. Your task is to find the first character in S that does not repeat anywhere else. A character is considered non-repeated if its frequency in the string is exactly one. If no such character exists, print None.

For example, in the string "swiss", the character 'w' is the first character that appears only once. In contrast, if every character repeats, the output should be None.

Note: The input will be provided as a single line via standard input, and the output should be written to standard output.

inputFormat

The input consists of a single line containing the string S. The string may be empty.

outputFormat

Output the first non-repeated character in S. If there is no such character, output None.

swiss

w