You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you today?

USER: Can you please book a flight ticket from Denver to Washington? As I have to reach there to meet my friend.

ASSISTANT: Sure, we are here to help you.

USER: Thank you.

ASSISTANT: Kindly share your travel dates.

USER: Sure, I have planned my travel dates as Dec 12 and Dec 14.

ASSISTANT: Please share your name.

USER: Sure, myself Rebecca Allen.

ASSISTANT: May I know your Washington airport code?

USER: I would prefer to reach DCA airport in Washington.

ASSISTANT: Do you have any connection limit?

USER: I am looking for single connecting flight.

ASSISTANT: Ok, please wait a moment.

USER: Sure but please consider DEN as my starting point airport code.

ASSISTANT: Ok.

USER: Thank you for that.

ASSISTANT: Sorry to say, no flights found with your requirement.

USER: Oh! It is sad to hear. Anyway, thank you for your time.

ASSISTANT: Thanks for reaching us.

USER: Most welcome.