Teacher: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
Teacher: Now, understand the problem? Solve this instance: customer: Hello. 
 agent: Hello, how can I help you today? 
 customer: Please help me in booking flight ticket from BOS to IAD. 
 agent: Sure, let me know your planned journey dates? 
 customer: My trip dates are Jan 20 to Jan 22. 
 agent: Do you have any connection limit? 
 customer: I need a connecting flight. 
 agent: Is there any other specifications? 
 customer: My depart should be in the evening. 
 agent: May I know your good name? 
 customer: Jonathan Harris. 
 agent: Thanks for your details, there is no flight found on your desired journey locations. 
 customer: Ok, no problem. Thank you. 
 agent: Thank you for availing us.
Student:
no_flight