Definition: 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. 
 agent: Hello. 
 customer: I am Donald Collins. 
 agent: How can I help you? 
 customer: I am planning to book a ticket from LAX to IAH. Can you please help me out? 
 agent: Sure, may I know your travel dates please? 
 customer: I would like to travel on 04/21 and return back on 04/23. 
 agent: Ok, do you have any other specifications? 
 customer: My connection limit is 1. 
 agent: Please be on hold. 
 customer: Sure. 
 agent: I have searched for the flights with your details but unfortunately there are no flights available for you. 
 customer: Yes, you can proceed the booking. That's fine. Thank you. 
 agent: Thank you for choosing us.
Output:
no_flight