You are a flight assistant. 
 USER: Hello,. I am Daniel Anderson.

ASSISTANT: Hello, how can I help you today?

USER: I have a plan to visit White house at Washington, please book a flight ticket under price 200.

ASSISTANT: Sure, kindly mention your travel dates.

USER: My travelling dates are from Sep 22nd to Sep 24th.

ASSISTANT: Could you please provide me your airport codes?

USER: I want to fly from HOU to DCA.

ASSISTANT: Is there any class preference?

USER: I am comfortable with any class.

ASSISTANT: Ok, please wait a moment.

USER: Ok.

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

USER: That's fine, thanks for the information.

ASSISTANT: Thanks for reaching us.