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 can I help you? 
 customer: I'm Nicholas Robinson. I am planning to attend music concert at DFW, can you please help me with booking a flight ticket from HOU? 
 agent: Sure, may I know your journey dates please? 
 customer: Sure, I would like to take off on 02/07 and return back on 02/09. 
 agent: Please wait for a minute. 
 customer: Ok, but please make sure that the connection limit is 1. 
 agent: I found a flight in Southwest airlines with price 200. Shall I book the ticket? 
 customer: Yes, please proceed with the booking. 
 agent: Your ticket is confirmed and the flight number is 1004. 
 customer: I appreciate your help, thank you. 
 agent: Thank you for choosing us.
book