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: Hi. 
 agent: Hello, how can I help you today? 
 customer: Can you please book a flight ticket from DEN to OAK? 
 agent: Sure, may I know your planned travel dates? 
 customer: My trip dates are 12/31 and 01/02. 
 agent: May I know your connection limit? 
 customer: I am comfortable to travel in a single connecting flight. 
 agent: Do you have any other specifications? 
 customer: I want to return in evening. 
 agent: Please wait for a moment. 
 customer: Sure. 
 agent: Sorry to say that, no flights were found with your given details. 
 customer: That's ok, thank you for your information. 
 agent: May I know your good name for documentation purpose? 
 customer: Alexander Mitchell here. 
 agent: Thank you for reaching us.
Output:
no_flight