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: I am Christopher Taylor. 
 agent: How can I help you? 
 customer: I planned to meet my cousin in DCA, can you please help me to book a flight ticket from PHL? 
 agent: Sure, can you please tell your travelling dates? 
 customer: I planned to travel on 02/18 and 02/20. 
 agent: Sorry, there are no flights available with your requested details. 
 customer: Ok, no problem. Thank you for your time. 
 agent: Thank you and have a nice day.
Output:
no_flight