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 may I help you? 
 customer: I am Mary Lee, want to travel from LAX to ATL. 
 agent: May I know your trip dates? 
 customer: My trip dates are from 08/27 to 08/29. 
 agent: In Frontier airline, there is a flight for you with 1 connection and fare is 100. Shall I proceed? 
 customer: Yes, please. 
 agent: Your ticket is booked. 
 customer: Thank you. 
 agent: Most welcome.
book