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: Hello. 
 agent: Hello, how can I assist you? 
 customer: I am a stand-up comedian, I have to host a show at Washington DC. So please book my ticket from Boston. 
 agent: Sure, I am here to help you. Could you please let me know your preferred airport codes? 
 customer: My itinerary dates are 09/12 and 09/14. 
 agent: Ok, may I know your source and destination airport codes? 
 customer: My airport codes are BOS and IAD. 
 agent: Ok, please wait for a while. 
 customer: Sure. 
 agent: There is a flight with single connection available in Delta airlines and the ticket fare is 100 only. Are you comfortable with this flight? 
 customer: Yes, please book my ticket. 
 agent: Your ticket is confirmed successfully and your flight number is 1027. 
 customer: Thank you. 
 agent: Ok, may I know your name? 
 customer: Patrick Young here. 
 agent: Your ticket is booked on the name of Patrick Young. 
 customer: Thanks. 
 agent: Thank you for choosing us.
book