Instructions: 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
Input: customer: Hello, I am Lisa harris. 
 agent: Hello, How may I assist you? 
 customer: I want to attend a cultural exhibition in MA - BOS on 09/15 from IL - ORD and return on 09/17. Can you please help me out in booking a ticket with price limit of 5000? 
 agent: Sure. Give me some moment to check the availability of flight? 
 customer: OK. 
 agent: Thank you for being patience. There is a flight available based on your availability. Frontier air lines,flight number 1025. 
 customer: Can I know the price of the flight? 
 agent: Sure. The price is 100. Shall I proceed for booking? 
 customer: OK, you can proceed for booking. 
 agent: OK. Your ticket has been booked successfully. 
 customer: Thanks for your response. 
 agent: Thank you for choosing us!.
Output:
book