Sanitize User Message

You are given a string message as input. Your task is to remove all characters from the string that are not allowed. The allowed characters are:

• All lowercase and uppercase English letters (a-z, A-Z)
• Digits (0-9)
• The space character ( )
• Punctuation marks: .,!?

In other words, if a character is not one of those listed above, it should be removed from the output. For example, the apostrophe (') and symbols such as @, #, $, etc., should be removed.

Formally, if you denote the input string by message, then the output string result is given by:

\[ result = \text{Concatenation of all } c \in message \text{ such that } c \in \{a-z, A-Z, 0-9, \text{ space}, \text{'.'}, ',', '!', '?'\} \]

Make sure your program reads input from STDIN and writes the result to STDOUT.

inputFormat

The input consists of a single line containing the string message. The string may include spaces and punctuation.

outputFormat

Output the sanitized string after removing all disallowed characters.

Hello, World! How's everything going @ your side?

Hello, World! Hows everything going  your side