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: My name is William Collins. 
 agent: How can I help you today? 
 customer: I have a business meeting in Los Angeles. Can you help me for booking a flight? 
 agent: Sure, can you please share your travel dates? 
 customer: My travelling dates are from 02/22 till 02/24. 
 agent: Ok, may I know your airport codes? 
 customer: My travelling airport codes are from DCA to LAX. 
 agent: Sorry, no flights are available on your route. 
 customer: It's ok, thank you for your information. 
 agent: Welcome, have a nice day.
Output:
no_flight