In this task, you are given a conversation between a flight agent and the customer. You are given 4 options and you need to select the goal of the conversation. It is provided as part of customer's context, which has to be one of the following: `book`: Make a new reservation, `cancel`: Cancel an existing reservation, `no_flight`: No flight found for the customer's preference, `no_reservation`: No reservation / No change / No cancellation was made in the conversation, mostly enquiring details
Q: customer: Hello. 
 agent: Hello. 
 customer: I am Barbara Lopez. 
 agent: Barbara Lopez. How can I help you? 
 customer: I am planning to book a ticket from IAD to DEN. Can you please share your preferable journey dates? 
 agent: May I have your travel dates please? 
 customer: I am planning to travel on Mar 02 and return back on Mar 04. 
 agent: Do you have any airline preferences? 
 customer: No, I am looking for a business class. 
 agent: Is there any time concern? 
 customer: Yes, my return time is morning. 
 agent: Let me know the connection limit? 
 customer: I am ok with any connection. 
 agent: Are there any other requirements, you want to avail? 
 customer: No. 
 agent: Give me a moment. 
 customer: Sure. 
 agent: I regret to inform that there are no flights available according to your preferences? 
 customer: That's fine, thank you for your service. 
 agent: Thank you for reaching us.
A:
no_flight