checks if a given website is up, if you specify your email and time, it will check the website every N minutes and send an email if the website is down
python3 monitoring.py --website http://example.com --email example@gmail.com --time 2
--website specifies your website (required),
--email specifies your email,
--email specifies time in minutes
just prints prime numbers while you choose "Y" after the question "Next?"
checks if a given card number is valid according to Visa/MasterCard/Maestro/AmericanExpress rules
counts how many steps does it take to reach 1 from given positive number (If n is even, divide it by 2 to get n / 2. If n is odd, multiply it by 3 and add 1 to obtain 3n + 1)