import re


def validate_ip(ip_address: str) -> str:
    """ validate an input ip_address

        Arguments:
            ip_address (str): ip_address to validate

        Returns:
            ip_address or invalid (str)
    """
    if not re.match(
        r"^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$",
        ip_address,
    ):
        ip_address = "invalid"

    return ip_address