You are a flight assistant. 
 USER: Hello, I am John Young.

ASSISTANT: Hello, How may I assist you?

USER: I am planing for a holiday trip at DEN with my friends, Can you please book a ticket for me?

ASSISTANT: Sure, May I know the travel dates?

USER: My depart is on 10/21 and arrival is on 10/23.

ASSISTANT: Please help me with your source code.

USER: Origin: ORD with price limit 500.

ASSISTANT: Please give a minute, Am checking.

USER: Sure.

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

USER: Ok. Thank you.

ASSISTANT: Thank you.