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. 
 customer: I am Timothy Martin. 
 agent: How may I help you? 
 customer: I need to book a flight ticket from New York, NY-EWR to Boston, MA-BOS. 
 agent: Sure, help me with the travel dates? 
 customer: I want to travel on dates 10/16 and 10/18. 
 agent: We do not found any flights running in your preferred routes. 
 customer: No problem, thank you for your help. 
 agent: Thank you for opting us.
Student:
no_flight