You will be given a definition of a task first, then an example. Follow the example to solve a new instance 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: Hi. 
 agent: Hello. How can I help you? 
 customer: I would like to change my existing reservation as my plan to go for a holiday trip got postponed. Can you please help me with this? 
 agent: Sure, may I know your name please? 
 customer: My name is Anthony Phillips. 
 agent: Please wait a moment. 
 customer: Sure. 
 agent: Unfortunately there is no reservation found with your given name. 
 customer: Not a problem, thank you for checking. 
 agent: Thank you for choosing us.
Solution: no_reservation
Why? Here the customer has not asked for any booking, he just wanted to update his already booked flight, so the status would be no_reservation

New input: customer: Hi. 
 agent: Hello. 
 customer: Brian Walker here. 
 agent: How may I help you Brian? 
 customer: I want to attend a birthday party in New York. Will you please book my ticket? 
 agent: Ok, can you provide me New York airport code? 
 customer: Airport codes are SFO and LGA. 
 agent: May I know your travelling dates? 
 customer: I want to depart on 12/09 and return by 12/11. 
 agent: There is a flight with 1 connected flight which costs 200. Flight 1003 in AA airline. 
 customer: Ok, please proceed for booking. 
 agent: Shall I book it for you? Your booking is done. 
 customer: Thank you for your service. 
 agent: Thank you for choosing us.
Solution:
book