Normalize Text

Clean up s like this:

1. Make every letter lower case.
2. Treat every character that is not a letter (a-z) or a digit (0-9) as a separator.
3. Join the pieces with single spaces, with no space at the start or end.

Example: " Hello, World!! 42 " becomes "hello world 42".

Examples

Example 1

Input:

normalize_text('  Hello,   World!! 42 ')

Output:

'hello world 42'

Example 2

Input:

normalize_text('---')

Output:

''

Constraints

• 0 <= len(s) <= 3 * 10**5
• s contains only printable ASCII characters.