Write a quick password validator to make sure that the people that visit your site use appropriate passwords.

Respond with "VALID" if the string meets the requirements or "INVALID" if it does not.

Requirements:
More than 3 characters but less than 20.
Must contain only alphanumeric characters.
Must contain letters and numbers.

Examples
'Username123!' => INVALID
'123' => INVALID
'Username123' => VALID

Tests
'Username'
'IsThisPasswordTooLong'
'DEVCommunity'

Good luck!

This challenge comes from jhoffner on CodeWars. Thank you to CodeWars, who has licensed redistribution of this challenge under the 2-Clause BSD License!

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