Q: 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
customer: Hello. 
 agent: Hello. How can I assist you? 
 customer: Myself Charles Wilson, I need to attend a metting at Denver.Could you help me by booking a ticket? 
 agent: Sure, can I know the travel dates please? 
 customer: I am willing to travel on 05/20 and again I will retrive on 05/22. 
 agent: Could you please provide the airport codes? 
 customer: My departure and destination airport codes are ATL to DEN. 
 agent: Sorry, there are no flights available on your route. 
 customer: Not a big deal, anyway thank you very much for your service. 
 agent: Thank you for approaching us.
A:
no_flight