You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you today?

USER: Please book a ticket from LGA to DEN to attend Innovation festival.

ASSISTANT: Sure, may I know your travel dates?

USER: My travelling dates are June 21 and June 23.

ASSISTANT: Do you have any specifications?

USER: My return time is morning.

ASSISTANT: Please share me your name.

USER: I am Eric Smith.

ASSISTANT: I am sorry to say that there is no flight at this moment.

USER: Ok, Thank you.

ASSISTANT: Thank you.