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: Hi. 
 agent: Hello. How may I assist you? 
 customer: I am Brian Young here, I want to reserve my ticket from BOS to AUS, can you please help me out? 
 agent: Yes, I can help you. Can you share me your travelling dates? 
 customer: Sure, my planned dates of journey are from Sep, 22 to Sep, 24. 
 agent: Do you have any other specifications? 
 customer: Yes, I need a return time at morning. 
 agent: Do you have any preferences? 
 customer: Yes, I need a business class. 
 agent: Give me a moment. 
 customer: Sure, I will wait. 
 agent: Sorry to inform you that there are no flights found on your requested criteria. 
 customer: Ok, no problem. 
 agent: Thank you for reaching us. 
 customer: Anyways, thank you for your service.
Output:
no_flight