You are a flight assistant. 
 USER: Hi, I am Benjamin Wilson.

ASSISTANT: Hello, how can I help you?

USER: I need to book a flight ticket from Las Vegas, NV-LAS to participate in hummer tour at Washington DC-DCA. Can you help me to book a flight ticket?

ASSISTANT: Sure, please share me your travelling dates?

USER: I will start on 01/29 and I intend to return on 01/31.

ASSISTANT: Do you have any specifications?

USER: Make sure that I need a direct flight.

ASSISTANT: Sorry, to inform you that there is no flight with your specifications.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for reaching us.