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: Myself Kevin Johnson. 
 agent: Kevin, how can I assist you? 
 customer: Can you please help me in booking a flight ticket from DEN to EWR locations? 
 agent: Sure, may I know your trip dates? 
 customer: My travelling dates are from 07/02 and 07/04. 
 agent: Please hold on for a moment. 
 customer: Ok. 
 agent: Sorry, no flight is available on your route. 
 customer: It's ok. Thank you for the information. 
 agent: Thank you for choosing us.
Output:
no_flight