You will be given a definition of a task first, then some input of the task.
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? 
 customer: I am William Anderson. I need to visit Lyndon Baines Johnson library at Austin. Can you book me a flight ticket? 
 agent: Sure, I will help you in that. 
 customer: Thank you. 
 agent: When did you planned to visit Lyndon Baines Johnson library? 
 customer: I want to travel on 04/18, and need to catch return flight on 04/20. 
 agent: Thanks for providing your dates we need some more details also, please share me your airport codes? 
 customer:  I need to leave from my nearest airport HOU to reach AUS. 
 agent: We found a flight on your details with airline Spirit, flight number: 1026. Shall I book this ticket with economy flight? 
 customer: Proceed with the booking. 
 agent: Your ticket has been booked. 
 customer: Thanks for the help. 
 agent: Thank you so much.
Output:
book