You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you for the day?

USER: Myself Robert Smith. I would like to visit the Washington cities, can you help me in booking the flight ticket from DEN to IAD?

ASSISTANT: Sure, I am here to help you.

USER: Sure, I will start my journey on 05/20 and return will be on 05/22.

ASSISTANT: Please wait for a moment.

USER: Ok, I will wait for your response.

ASSISTANT: Sorry, we found no flights on your given dates.

USER: That's ok, no problem. Thank you for the information.

ASSISTANT: Thank you for reaching us. Hope to serve you better next time.