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 can I assist you at this moment? 
 customer: I need to travel from BOS to DCA, can you help me in that? 
 agent: sure, I will help you with that. Can I have your travel dates please? 
 customer: My trip dates are Nov 15 to 17. 
 agent: Ok,  please let me know your preferable class. 
 customer: I am comfortable in any class. 
 agent: Do you  have any other specifications? 
 customer: Please ensure that my depart time is in afternoon. 
 agent: Can I have your good name please? 
 customer: Brian Phillips here. 
 agent: Sorry to inform you that no flight is available to you on your planned dates. 
 customer: Ok, no issues. Thank you for the information. 
 agent: Thank you for choosing us, have a good day.
Output:
no_flight