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. I'm Nancy Nelson. 
 agent: Hello. How can I help you? 
 customer: I am planning to attend music concert at LGA, can you please help me with booking a flight ticket from DEN? 
 agent: May I know your desired travel dates please? 
 customer: Sure, I would like to take off on 06/18 and return back on 06/20. 
 agent: There is no flight available on your desired travel dates. 
 customer: Ok, no issues. Thank you for checking. 
 agent: Thank you for opting us. 
 customer: You are welcome.
A:
no_flight