You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, How can I assist you?

USER: Please help me to book a flight ticket from DEN to DCA?

ASSISTANT: Sure, May I know the travelling dates?

USER: My travelling dates are Nov 19 to Nov 21.

ASSISTANT: Do you have any connection limit?

USER: I need a single connection of flight.

ASSISTANT: Is there any other requirements?

USER: No.

ASSISTANT: May I know your name?

USER: I am Jacob Green.

ASSISTANT: Sorry, No flights found with your chosen dates.

USER: It's ok, thank you.

ASSISTANT: Thank you for opting us.