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: Hi. 
 agent: Hello, how can I help you? 
 customer: Brian Baker here. I want to book a flight on the route from SFO for my round trip, can you help me? 
 agent: May I know your desired travel dates please? 
 customer: My travelling dates will be from 08/26 to 08/28. 
 agent: There is a flight with connection limit 1 and fare 100, shall I proceed for booking? 
 customer: Please proceed with booking my reservation. 
 agent: Your ticket is booked, flight number 1004. 
 customer: Thank you for helping me with booking ticket. 
 agent: Thank you for opting us. 
 customer: You are most welcome.
book