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 aid you? 
 customer: I am Betty Perez. I would like to visit New York city to spend my vacation holidays with childhood friends. So please help me with flight ticket booking. 
 agent: Sure, I am here to help you. Could you please tell me your travel dates? 
 customer: Thank you. I need to travel on dates of 09/21 and 09/23. 
 agent: Ok, please help me with your source and destination airport codes. 
 customer: Sure, I would like to travel from SEA to EWR because these are the only airports which are near to my travelling locations. 
 agent: Ok, please wait for a moment. 
 customer: Sure, take your time to check. 
 agent: Sorry, there is no flight available on your preferred dates. 
 customer: Oh! It is sad to hear. Anyway, I will choose another agency this time. Thank you for your valuable time. 
 agent: You are welcome and thank you for choosing us.
no_flight