Detailed 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
Q: customer: Hello. 
 agent: Hello. How can I help you? 
 customer: My name is Gary Walker. I am searching for the flight which is departing in the morning time from Denver, can you please help me to book the flight ticket? 
 agent: Sure, I will help you to book a flight ticket. Can you please share me your travelling dates? 
 customer: Thank you for accepting my request. My planned travelling dates are Nov/16 and Nov/18. 
 agent: Ok, may I know your airport codes? 
 customer: The origin and destination airport codes are DEN and IAH. 
 agent: Please give me a moment. Here, I found a flight for you with single connection and ticket fare is 300 in economy class. 
 customer: I am looking for a business class flight which is returning in the evening time. So, please recheck for that. 
 agent: Sorry, no flights are available on your route. 
 customer: It's ok, not a problem with that. 
 agent: Thank you for choosing us. 
 customer: Thank you for your time. 
 agent: Welcome, have a nice day.
A:
no_flight