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The First Non Repeated Character In A String

You need to write a function, that returns the first non-repeated character in the given string.

For example for string "test" function should return 'e'.

For string "teeter" function should return 'r'.

If a string contains all unique characters, then return just the first character of the string.

Example: for input "trend" function should return 't'.

You can assume, that the input string has always non-zero length.

If there is no repeating character, return null in JS or Java, and None in Python.

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