You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, how can I assist you?

USER: Please book a flight to Denver, CO-DEN from Las Vegas, NV-LAS for holiday vacation.

ASSISTANT: Sure, please mention your travel dates?

USER: Travel dates are 12/12 to 12/14. I need a direct flight.

ASSISTANT: Ok, Is there any connection limit for you? Ok, please wait or a minute.

USER: Sure.

ASSISTANT: I regret, there is no flight available with your requirements.

USER: I am Katherine Hill. Thanks for the assistance.