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
Input: customer: Hello. 
 agent: Hello, how may I guide you? 
 customer: I am Alexander Wilson. Can you please book a flight ticket from CLT to DTW? 
 agent: Sure, I am here to help you out. Please provide me your trip dates. 
 customer: Yes, my travel dates are 04/19 and 04/21. 
 agent: Sorry Wilson, there is no flight in your route. 
 customer: That's ok, no problem. Thank you for your information. 
 agent: Thank you for reaching us.
Output:
no_flight