Given the task definition and input, reply with output. 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 may I assist you today? 
 customer: I am looking to reserve a flight ticket to reach Las Vegas, can you please find a flight with the connection limit 1? 
 agent: Sure, may I know your airport codes please? 
 customer: The preferred airport codes are DFW and LAS. 
 agent: Thank you, may I know your planned travel dates? 
 customer: The scheduled travel dates are Dec 19 and Dec 21. 
 agent: Do you have any class preference? 
 customer: I need a business class flight to reach my destination. 
 agent: May I know your name for booking purpose? 
 customer: My name is Timothy Collins. 
 agent: Do you want any another specifications? 
 customer: No, I have mentioned all my specifications. 
 agent: Unfortunately, no flights available on your requirements. 
 customer: It's ok, not a problem with that. Anyways thank you for your time. 
 agent: Welcome, thank you for reaching us.
no_flight