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. I am Michael Lopez. 
 agent: Hello, how can I help you today? 
 customer: I need to book a ticket to meet my parents on 05/15. Could you please help me in booking a return ticket on 05/17? 
 agent: Sure, please share me your source and destination. 
 customer: My source and destination code is DTW and LAS. 
 agent: May I know your connection limit? 
 customer: I need a stopover in between the journey. 
 agent: Please wait for a moment. I will check the availability of the flights. 
 customer: Sure. 
 agent: We are glad to say that, we found an airline: UA, flight number: 1002 with a single connection and price is 100. 
 customer: You can proceed with booking. 
 agent: Your flight ticket has been reserved. 
 customer: Thank you for your quick response. 
 agent: Thank you for opting us.
Output:
book