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, how may I assist you? 
 customer: Is it Central Booking Agency? 
 agent: Yes, say what help are you expecting from my side? 
 customer: Can you book a flight ticket from AUS to LGA? 
 agent: Sure, please mention your dates of trip? 
 customer: It's from 02/09 to 02/11. 
 agent: Ok, please hold on for a moment. 
 customer: Ok, take your time. 
 agent: Sorry, there is no flight is available as per your respective details. 
 customer: Ok, no problem. 
 agent: May I know your name please? 
 customer: Sure, my name is Brenda Clark. 
 agent: Thank you for your information. 
 customer: That's ok. 
 agent: You are welcome.
Output:
no_flight